Cbse | Class 12 Science Pcb | Biology | Molecular Basis Of Inheritance | Mock Tests, Notes & MCQs

BhamuIntelli Systems LLP

StudyTunnel

Loading content...

Multiple Choice Questions

Increased protein synthesis

Decreased mRNA transcription

Inhibition of peptide bond formation

Enhanced ribosomal assembly

Correct Answer: C

Solution:

The 23S rRNA is crucial for catalyzing peptide bond formation. A mutation impairing this function would inhibit the ribosome's ability to synthesize proteins.

Chapter Concept:

Ribosome and Peptide Bond Formation

Transcription would initiate at the terminator and end at the promoter.

The coding and template strands would be reversed, potentially altering the gene expression.

RNA polymerase would bind more efficiently, increasing transcription rate.

There would be no effect on the transcription process.

Correct Answer: B

Solution:

Switching the promoter with the terminator sequence would reverse the definition of coding and template strands, potentially altering gene expression as the wrong strand may be transcribed.

Chapter Concept:

Transcription Unit

Griffith's experiment with Streptococcus pneumoniae.

Avery, MacLeod, and McCarty's demonstration of DNA as the transforming principle.

Hershey and Chase's experiment with bacteriophages.

Meselson and Stahl's experiment using isotopic nitrogen.

Correct Answer: D

Solution:

Meselson and Stahl's experiment used isotopic nitrogen to show that DNA replication is semiconservative, with each new DNA molecule containing one old and one new strand.

Chapter Concept:

Semiconservative Replication

DNA lacks a 2'-OH group, making it less reactive.

RNA contains thymine, which provides stability.

DNA is single-stranded, which enhances its stability.

RNA is double-stranded, making it more stable.

Correct Answer: A

Solution:

DNA is more stable than RNA because it lacks the 2'-OH group present in RNA, which makes RNA more reactive and less stable.

Chapter Concept:

DNA versus RNA as Genetic Material

The genetic code is degenerate, meaning multiple codons can code for the same amino acid.

The genetic code is universal, meaning all organisms use the same codons for amino acids.

The genetic code includes stop codons that do not code for any amino acids.

The genetic code is non-overlapping, meaning each nucleotide is part of only one codon.

Correct Answer: A

Solution:

Reverse prediction is ambiguous because the genetic code is degenerate, allowing multiple codons to code for the same amino acid, making it impossible to determine the exact mRNA sequence from a protein sequence.

Chapter Concept:

Codon Table and Amino Acid Prediction

Ability to replicate

Chemical and structural stability

Ability to express Mendelian characters

Ability to be easily degraded

Correct Answer: D

Solution:

Genetic material must be stable and not easily degraded to ensure accurate transmission of genetic information across generations.

Chapter Concept:

Properties of Genetic Material

tRNA acts as a catalyst for peptide bond formation.

tRNA serves as the template for protein synthesis.

tRNA brings amino acids to the ribosome and matches them with the codons on mRNA.

tRNA is responsible for transcribing DNA into mRNA.

Correct Answer: C

Solution:

tRNA functions as an adapter molecule that brings specific amino acids to the ribosome and matches them with the appropriate codons on the mRNA during translation.

Chapter Concept:

Genetic Code and Translation

The genetic code is triplet and degenerate.

The genetic code is overlapping and discontinuous.

The genetic code is specific to humans only.

The genetic code uses UAA, UAG, UGA as start codons.

Correct Answer: A

Solution:

The genetic code is characterized by being triplet, degenerate, nearly universal, non-overlapping, continuous, read in mRNA, and includes AUG as the start codon and UAA, UAG, UGA as stop codons.

Chapter Concept:

Genetic Code Features

It changes a single amino acid in the protein.

It causes the insertion or deletion of a single nucleotide, altering the reading frame.

It results in the addition of a stop codon, terminating protein synthesis prematurely.

It replaces one amino acid with another without altering the reading frame.

Correct Answer: B

Solution:

A frameshift mutation involves the insertion or deletion of nucleotides that are not in multiples of three, which shifts the reading frame and alters the entire amino acid sequence downstream.

Chapter Concept:

Mutations and Genetic Code

i gene

z gene

y gene

a gene

Correct Answer: B

Solution:

The z gene codes for beta-galactosidase, which is responsible for the hydrolysis of lactose into glucose and galactose.

Chapter Concept:

Gene Regulation and Lac Operon

A change in the reading frame leading to a completely different sequence of amino acids.

A single amino acid change without affecting the reading frame.

The addition of a stop codon at the beginning of the sequence.

No change in the protein sequence as silent mutations occur.

Correct Answer: A

Solution:

Frameshift mutations involve the insertion or deletion of nucleotides that are not in multiples of three, which alters the reading frame and results in a different sequence of amino acids.

Chapter Concept:

Mutations and Genetic Code

Point mutation; Glutamate to Valine

Frameshift mutation; Glutamate to Glycine

Insertion mutation; Valine to Glutamate

Deletion mutation; Valine to Glycine

Correct Answer: A

Solution:

Sickle-cell anemia is caused by a point mutation in the gene coding for the beta globin chain, which results in the substitution of glutamate with valine.

Chapter Concept:

Mutations and Genetic Code

3.3 million bp

3164.7 million bp

30,000 bp

99.9 million bp

Correct Answer: B

Solution:

The human genome consists of approximately 3164.7 million base pairs.

Chapter Concept:

Salient Features of Human Genome

The human genome has a high percentage of repeated sequences.

The human genome is composed of approximately 30,000 genes.

The human genome has 99.9% similarity among different individuals.

The human genome is predominantly composed of protein-coding DNA.

Correct Answer: D

Solution:

The human genome is less than 2% protein-coding DNA, with a high percentage of non-coding and repeated sequences.

Chapter Concept:

Salient Features of Human Genome

It showed that proteins are the genetic material.

It demonstrated that RNA is the genetic material.

It identified DNA as the genetic material responsible for transformation.

It proved that lipids are the genetic material.

Correct Answer: C

Solution:

The experiment by Avery, MacLeod, and McCarty showed that only DNA from heat-killed S cells could transform R cells into S cells, proving DNA is the genetic material.

Chapter Concept:

Avery-MacLeod-McCarty Experiment

Methionine-Phenylalanine-Phenylalanine-Phenylalanine-Phenylalanine

Methionine-Phenylalanine-Leucine-Leucine-Phenylalanine

Methionine-Leucine-Leucine-Phenylalanine-Phenylalanine

Methionine-Phenylalanine-Phenylalanine-Serine-Phenylalanine

Correct Answer: A

Solution:

The mRNA sequence codes for the amino acids Methionine (AUG), Phenylalanine (UUU), Phenylalanine (UUC), Phenylalanine (UUC), Phenylalanine (UUU), Phenylalanine (UUU), and Phenylalanine (UUC) according to the genetic code table.

Chapter Concept:

Codon Table and Amino Acid Prediction

Methionine-Phenylalanine-Phenylalanine-Phenylalanine-Phenylalanine-Phenylalanine

Methionine-Valine-Valine-Valine-Valine-Valine-Valine

Methionine-Leucine-Leucine-Leucine-Leucine-Leucine-Leucine

Methionine-Isoleucine-Isoleucine-Isoleucine-Isoleucine-Isoleucine

Correct Answer: A

Solution:

The mRNA sequence codes for the amino acids Methionine (AUG) and Phenylalanine (UUU and UUC), resulting in the sequence Methionine-Phenylalanine-Phenylalanine-Phenylalanine-Phenylalanine-Phenylalanine.

Chapter Concept:

Mutations and Genetic Code

The genetic code is a triplet code, where each codon specifies one amino acid.

The genetic code is non-degenerate, with each amino acid being coded by a single codon.

The genetic code is different for prokaryotes and eukaryotes.

The genetic code includes punctuation marks between codons.

Correct Answer: A

Solution:

The genetic code is a triplet code, meaning each codon consists of three nucleotides that specify a single amino acid. It is degenerate, meaning multiple codons can code for the same amino acid, and it is nearly universal across organisms.

Chapter Concept:

Genetic Code and Translation

To prevent the formation of double-stranded RNA, which would hinder translation.

Because the other strand is not accessible to RNA polymerase.

To ensure that both strands produce identical RNA molecules.

Because the coding strand is chemically unstable.

Correct Answer: A

Solution:

If both strands were used as templates, they would produce complementary RNA molecules that could pair to form double-stranded RNA, preventing translation.

Chapter Concept:

Central Dogma of Molecular Biology

Radioactive sulfur was used to label DNA.

Radioactive phosphorus was used to label proteins.

Radioactive phosphorus was used to label DNA.

Radioactive sulfur was used to label RNA.

Correct Answer: C

Solution:

In the Hershey-Chase experiment, radioactive phosphorus (

^{32}P

) was used to label DNA because DNA contains phosphorus, while radioactive sulfur (

^{35}S

) was used to label proteins.

Chapter Concept:

Properties of Genetic Material

DNA replicates conservatively.

DNA replicates semiconservatively.

DNA replicates dispersively.

DNA does not replicate.

Correct Answer: B

Solution:

The Meselson-Stahl experiment demonstrated that DNA replication is semiconservative, as each daughter DNA molecule consists of one parental and one newly synthesized strand.

Chapter Concept:

Meselson-Stahl Experiment

RNA is more stable than DNA due to its double-stranded nature.

RNA can act as a catalyst and mutates faster than DNA.

RNA is less reactive than DNA, making it more suitable for long-term storage of genetic information.

RNA contains thymine, which stabilizes its structure.

Correct Answer: B

Solution:

RNA is considered more dynamic because it can act as a catalyst and mutates faster than DNA, which is more stable due to its lack of the 2'-OH group and presence of thymine.

Chapter Concept:

DNA versus RNA as Genetic Material

Each daughter DNA molecule contains two newly synthesized strands.

Each daughter DNA molecule contains one parental strand and one newly synthesized strand.

Each daughter DNA molecule contains two parental strands.

Each daughter DNA molecule contains a random mixture of parental and newly synthesized strands.

Correct Answer: B

Solution:

Semiconservative replication means that each daughter DNA molecule consists of one strand from the original DNA molecule and one newly synthesized strand, ensuring genetic continuity.

Chapter Concept:

Semiconservative Replication

Radioactive sulfur (

^{35}S

)

Radioactive phosphorus (

^{32}P

)

Radioactive carbon (

^{14}C

)

Radioactive nitrogen (

^{15}N

)

Correct Answer: B

Solution:

The Hershey-Chase experiment used radioactive phosphorus (

^{32}P

) to label the DNA because DNA contains phosphorus but not sulfur.

Chapter Concept:

Hershey-Chase Experiment

Uracil forms stronger hydrogen bonds with adenine than thymine does.

The absence of thymine in RNA makes it more stable than DNA.

The presence of uracil makes RNA more reactive and less stable than DNA.

Uracil allows RNA to form a double helix similar to DNA.

Correct Answer: C

Solution:

Uracil in RNA makes it more reactive and less stable compared to DNA, which contains thymine. This is due to the additional -OH group in RNA and the lack of methylation that occurs in thymine, contributing to DNA's stability.

Chapter Concept:

Polynucleotide Chain Structure

It provides a binding site for RNA polymerase.

It terminates the process of transcription.

It is the site where translation begins.

It is the sequence that gets transcribed into RNA.

Correct Answer: A

Solution:

The promoter is a DNA sequence that provides the binding site for RNA polymerase, initiating the transcription process.

Chapter Concept:

RNA and Transcription

To identify and sequence small RNA molecules.

To locate expressed genes by sequencing cDNA derived from mRNA.

To map the entire genome using only non-coding regions.

To synthesize artificial genes for experimental purposes.

Correct Answer: B

Solution:

EST (Expressed Sequence Tag) based gene identification involves sequencing cDNA derived from mRNA, which helps in locating expressed genes and understanding gene expression patterns.

Chapter Concept:

HGP Methodologies

Live R strain and heat-killed S strain

Live S strain and heat-killed R strain

Heat-killed S strain only

Live R strain only

Correct Answer: A

Solution:

Griffith observed that when live R strain bacteria were mixed with heat-killed S strain bacteria, the mice died. This indicated that some 'transforming principle' from the heat-killed S strain transformed the R strain into a virulent form.

Chapter Concept:

DNA as Genetic Material: Griffith Experiment

22%

28%

56%

44%

Correct Answer: B

Solution:

Chargaff's Rule states that in double-stranded DNA, the amount of adenine (A) equals thymine (T) and the amount of guanine (G) equals cytosine (C). If cytosine is 22%, then guanine is also 22%. This leaves 56% for adenine and thymine combined, hence thymine would be 28%.

Chapter Concept:

Chargaff’s Rule

It allows DNA polymerase to synthesize both strands continuously.

It enables the formation of hydrogen bonds between complementary bases.

It requires one strand to be synthesized continuously while the other is synthesized in fragments.

It prevents the DNA strands from being separated during replication.

Correct Answer: C

Solution:

The antiparallel nature of DNA strands means that one strand is oriented 5'-3' and the other 3'-5'. During replication, DNA polymerase can only synthesize DNA in the 5'-3' direction, leading to continuous synthesis on the leading strand and discontinuous synthesis on the lagging strand, forming Okazaki fragments.

Chapter Concept:

Polynucleotide Chain Structure

Heavy DNA

Light DNA

Hybrid DNA

No DNA

Correct Answer: C

Solution:

After one generation in

^{14}NH_4Cl

, the DNA extracted from

E. coli

showed hybrid density, indicating semiconservative replication.

Chapter Concept:

Meselson-Stahl Experiment

It enhances the binding of RNA polymerase to the promoter.

It binds to the operator region to prevent transcription.

It acts as an inducer for the operon.

It binds to the promoter to initiate transcription.

Correct Answer: B

Solution:

In the absence of lactose, the repressor protein binds to the operator region, preventing RNA polymerase from transcribing the operon.

Chapter Concept:

Gene Regulation and Lac Operon

They determine the direction of DNA replication.

They are involved in the formation of hydrogen bonds between bases.

They are the sites where amino acids are attached.

They are the binding sites for ribosomes during translation.

Correct Answer: A

Solution:

The 5' and 3' ends of a DNA molecule are crucial for determining the direction of DNA replication, as DNA polymerases can only add nucleotides to the 3' end.

Chapter Concept:

Polynucleotide Chain Structure

Addition of a poly-A tail

Splicing of introns

Addition of a 5' cap

Methylation of exons

Correct Answer: C

Solution:

In eukaryotic RNA processing, a 5' cap, which is a modified guanine nucleotide, is added to the 5' end of hnRNA to protect it from degradation and assist in ribosome binding during translation.

Chapter Concept:

RNA Processing in Eukaryotes

Adenine pairs with Thymine via three hydrogen bonds.

Guanine pairs with Cytosine via two hydrogen bonds.

Adenine pairs with Thymine via two hydrogen bonds.

Guanine pairs with Cytosine via four hydrogen bonds.

Correct Answer: C

Solution:

Adenine pairs with Thymine via two hydrogen bonds, while Guanine pairs with Cytosine via three hydrogen bonds.

Chapter Concept:

Purines, Pyrimidines and Base Pairing

RNA polymerase I

RNA polymerase II

RNA polymerase III

RNA polymerase IV

Correct Answer: B

Solution:

RNA polymerase II is responsible for transcribing mRNA precursors (hnRNA) in eukaryotic cells. A mutation affecting mRNA transcription would likely involve RNA polymerase II.

Chapter Concept:

Eukaryotic RNA Polymerases

The amount of adenine equals the amount of guanine.

The amount of adenine equals the amount of thymine.

The amount of cytosine equals the amount of thymine.

The amount of guanine equals the amount of uracil.

Correct Answer: B

Solution:

Chargaff's rule states that in double-stranded DNA, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.

Chapter Concept:

DNA Structure and Replication

Amino acids are linked by hydrogen bonds.

Amino acids are linked by disulfide bonds.

Amino acids are linked by peptide bonds formed through dehydration synthesis.

Amino acids are linked by ionic bonds.

Correct Answer: C

Solution:

During the elongation phase of translation, amino acids are linked together by peptide bonds, which are formed through a dehydration synthesis reaction catalyzed by the ribosome.

Chapter Concept:

Genetic Code and Translation

Each new DNA molecule consists of two newly synthesized strands.

Each new DNA molecule consists of one parental strand and one newly synthesized strand.

Each new DNA molecule consists of two parental strands.

Each new DNA molecule consists of randomly mixed parental and new strands.

Correct Answer: B

Solution:

In semiconservative replication, each daughter DNA molecule contains one parental strand and one newly synthesized strand, as per the Watson-Crick model.

Chapter Concept:

Semiconservative Replication

Replication

Chemical and structural stability

Slow mutation for evolution

Expression of Mendelian characters

Correct Answer: D

Solution:

The genetic material must be able to express Mendelian characters, which is one of its essential properties.

Chapter Concept:

Properties of Genetic Material

Replication occurs continuously on both strands.

Replication occurs continuously on the leading strand and discontinuously on the lagging strand.

Replication occurs discontinuously on both strands.

Replication occurs continuously on the lagging strand and discontinuously on the leading strand.

Correct Answer: B

Solution:

At the replication fork, the leading strand is synthesized continuously in the 5' to 3' direction, while the lagging strand is synthesized discontinuously in short fragments called Okazaki fragments.

Chapter Concept:

Replication Fork and DNA Polymerase

Nucleotides are linked by 3'-5' phosphodiester bonds, with a free 5' phosphate and a free 3' hydroxyl group.

Nucleotides are linked by 5'-3' phosphodiester bonds, with a free 3' phosphate and a free 5' hydroxyl group.

Nucleotides are linked by hydrogen bonds between the phosphate groups.

Nucleotides are linked by covalent bonds between nitrogenous bases.

Correct Answer: A

Solution:

In DNA, nucleotides are linked by 3'-5' phosphodiester bonds, resulting in a free 5' phosphate group at one end and a free 3' hydroxyl group at the other end of the chain.

Chapter Concept:

Polynucleotide Chain Structure

Protein is the genetic material of bacteriophages.

DNA is the genetic material of bacteriophages.

Both DNA and protein are genetic materials of bacteriophages.

Neither DNA nor protein is the genetic material of bacteriophages.

Correct Answer: B

Solution:

The Hershey-Chase experiment demonstrated that DNA is the genetic material because only the radioactive DNA entered the bacterial cells, not the protein.

Chapter Concept:

Hershey-Chase Experiment

A nucleosome consists of DNA wrapped around a histone octamer.

A nucleosome consists of RNA wrapped around a histone octamer.

A nucleosome consists of DNA wrapped around a non-histone chromosomal protein.

A nucleosome consists of RNA wrapped around a non-histone chromosomal protein.

Correct Answer: A

Solution:

In eukaryotic cells, DNA is wrapped around a core of eight histone proteins to form a nucleosome, which is the fundamental unit of chromatin structure.

Chapter Concept:

Packaging of DNA

It encodes the enzyme beta-galactosidase.

It acts as an inducer for the operon.

It encodes the repressor protein that binds to the operator.

It increases the permeability of the cell to lactose.

Correct Answer: C

Solution:

The 'i' gene encodes the repressor protein that binds to the operator region of the lac operon, preventing transcription in the absence of an inducer.

Chapter Concept:

RNA and Transcription

It terminates transcription.

It initiates transcription by guiding RNA polymerase to the promoter.

It elongates the RNA strand.

It stabilizes the DNA double helix.

Correct Answer: B

Solution:

The sigma factor is essential for the initiation of transcription as it helps RNA polymerase recognize the promoter regions on the DNA.

Chapter Concept:

DNA Structure and Replication

5'-TACGTACG-3'

5'-GCATGCAT-3'

5'-CATGCATG-3'

5'-GCTAGCTA-3'

Correct Answer: B

Solution:

The complementary strand is formed by pairing adenine with thymine and guanine with cytosine, resulting in the sequence 5'-GCATGCAT-3'.

Chapter Concept:

Salient Features of DNA Double Helix

5'-AUGCAUGCAUGC-3'

5'-UACGUACGUACG-3'

5'-GCAUGCAUGCAU-3'

5'-CGUACGUACGUA-3'

Correct Answer: A

Solution:

The RNA sequence transcribed from the template strand (3'-ATGCATGCATGC-5') is 5'-AUGCAUGCAUGC-3', as RNA polymerase uses the template strand to synthesize RNA in the 5' to 3' direction, replacing thymine with uracil.

Chapter Concept:

Template Strand and Coding Strand

Sigma factor

Rho factor

RNA polymerase

Promoter

Correct Answer: B

Solution:

The rho factor is responsible for the termination of transcription in bacteria by facilitating the release of the nascent RNA from the DNA template.

Chapter Concept:

Bacterial Transcription

The two chains are coiled in a left-handed fashion.

It is made of two polynucleotide chains with a sugar-phosphate backbone.

The bases in two strands are paired through hydrogen bonds.

The two chains have antiparallel polarity.

Correct Answer: A

Solution:

The DNA double helix is right-handed, not left-handed. All other options describe correct features of the DNA double helix.

Chapter Concept:

Salient Features of DNA Double Helix

Lactose acts as an inducer by binding to the repressor, allowing transcription of the operon.

Lactose binds directly to the operator, preventing the repressor from binding.

Lactose enhances the binding of RNA polymerase to the promoter, increasing transcription.

Lactose inhibits the synthesis of the repressor protein.

Correct Answer: A

Solution:

Lactose acts as an inducer by binding to the repressor protein, inactivating it. This allows RNA polymerase to access the promoter and transcribe the operon.

Chapter Concept:

Lac Operon Structural Genes

Repressor

Inducer

Operator

Promoter

Correct Answer: B

Solution:

Lactose acts as an inducer in the lac operon system. It binds to the repressor, causing a conformational change that prevents the repressor from binding to the operator, thereby allowing transcription to proceed.

Chapter Concept:

Types of RNA

Transcription

Reverse Transcription

Translation

Replication

Correct Answer: B

Solution:

Reverse transcription is the process where genetic information flows from RNA to DNA, contrary to the usual flow in the Central Dogma.

Chapter Concept:

Central Dogma of Molecular Biology

DNA polymerase

DNA ligase

Helicase

Primase

Correct Answer: B

Solution:

DNA ligase is responsible for joining Okazaki fragments on the lagging strand during DNA replication.

Chapter Concept:

DNA Structure and Replication

DNA polymerase

Helicase

DNA ligase

Primase

Correct Answer: C

Solution:

DNA ligase is responsible for joining the Okazaki fragments on the lagging strand during DNA replication.

Chapter Concept:

Leading and Lagging Strand Synthesis

EST-based gene identification

Protein sequencing

RNA interference

CRISPR-Cas9

Correct Answer: A

Solution:

The Human Genome Project (HGP) used EST-based gene identification as one of its methodologies.

Chapter Concept:

HGP Methodologies

UAA

AUG

UGA

UAG

Correct Answer: B

Solution:

AUG is the start codon in the genetic code, which also codes for Methionine.

Chapter Concept:

Genetic Code and Translation

Cytosine

Thymine

Guanine

Uracil

Correct Answer: B

Solution:

Chargaff's Rule states that in double-stranded DNA, the amount of adenine (

A

) is equal to the amount of thymine (

T

), and the amount of guanine (

G

) is equal to the amount of cytosine (

C

Chapter Concept:

Chargaff’s Rule

Prokaryotic DNA is packaged into chromatin fibers using histones.

Prokaryotic DNA is organized into a nucleoid with the help of positively charged proteins.

Prokaryotic DNA is linear and wrapped around nucleosomes.

Prokaryotic DNA is circular and wrapped around non-histone chromosomal proteins.

Correct Answer: B

Solution:

In prokaryotes, DNA is organized into a nucleoid structure, where the negatively charged DNA is held with positively charged proteins.

Chapter Concept:

Packaging of DNA

Stop codons signal the end of translation and do not code for any amino acids.

Stop codons are recognized by special tRNAs that do not carry amino acids.

Stop codons are only recognized by DNA polymerase.

Stop codons are converted into start codons by ribosomes.

Correct Answer: A

Solution:

Stop codons do not code for any amino acids and are recognized by release factors, which terminate translation by releasing the newly synthesized polypeptide chain from the ribosome.

Chapter Concept:

tRNA as Adapter Molecule

Introns are removed by DNA polymerase.

Introns are removed by the spliceosome complex.

Introns are removed by RNA polymerase I.

Introns are removed by ribosomes.

Correct Answer: B

Solution:

Introns are removed from the pre-mRNA by a complex known as the spliceosome, which is composed of small nuclear RNAs and associated proteins, allowing the exons to be joined together.

Chapter Concept:

RNA Processing in Eukaryotes

BAC/YAC vectors were used to clone large DNA fragments for sequencing.

BAC/YAC vectors were used to increase the replication speed of DNA.

BAC/YAC vectors were used to synthesize proteins directly from DNA.

BAC/YAC vectors were used to identify mutations in RNA sequences.

Correct Answer: A

Solution:

BAC (Bacterial Artificial Chromosome) and YAC (Yeast Artificial Chromosome) vectors were crucial in the Human Genome Project for cloning large fragments of DNA, which facilitated the sequencing and mapping of the human genome.

Chapter Concept:

HGP Methodologies

mRNA

rRNA

tRNA

DNA

Correct Answer: C

Solution:

tRNA acts as the adapter molecule that reads the codons on mRNA and brings the corresponding amino acids for protein synthesis.

Chapter Concept:

Genetic Code and Translation

DNA lacks the 2'-OH group present in RNA.

DNA contains uracil instead of thymine.

RNA is double-stranded, providing more repair potential.

RNA is less reactive due to its structure.

Correct Answer: A

Solution:

DNA is more stable than RNA because it lacks the 2'-OH group present in RNA, which makes RNA more reactive and less stable.

Chapter Concept:

DNA versus RNA as Genetic Material

The human genome contains approximately 3164.7 million base pairs.

More than 50% of the human genome codes for proteins.

The human genome has about 60,000 genes.

There is less than 90% similarity among human genomes.

Correct Answer: A

Solution:

The human genome contains approximately 3164.7 million base pairs, less than 2% of which codes for proteins, and it has about 30,000 genes with 99.9% similarity among humans.

Chapter Concept:

Salient Features of Human Genome

Exons are sequences that are removed during RNA splicing.

Exons are sequences that appear in mature RNA after splicing.

Exons are non-coding sequences that regulate gene expression.

Exons are sequences that are transcribed but not translated.

Correct Answer: B

Solution:

Exons are the coding sequences in eukaryotic genes that are retained in the mature RNA after the splicing process, allowing them to be translated into proteins.

Chapter Concept:

Exons, Introns and Split Genes

Protease

RNase

DNase

Lipase

Correct Answer: C

Solution:

The Avery-MacLeod-McCarty experiment demonstrated that DNA is the transforming principle because only DNase, which digests DNA, inhibited the transformation of R cells into S cells.

Chapter Concept:

Avery-MacLeod-McCarty Experiment

Splicing

Capping

Tailing

Replication

Correct Answer: D

Solution:

Replication is not part of RNA processing. RNA processing involves splicing, capping, and tailing.

Chapter Concept:

RNA Processing in Eukaryotes

DNA replication

DNA fingerprinting

Protein synthesis

RNA transcription

Correct Answer: B

Solution:

VNTRs are highly polymorphic minisatellite DNA sequences that are primarily used in DNA fingerprinting due to their variable copy number among individuals.

Chapter Concept:

VNTR and DNA Polymorphism

DNA is scattered throughout the cell.

DNA is organized into nucleoid loops.

DNA is wrapped around histone octamers to form nucleosomes.

DNA is condensed into a single strand.

Correct Answer: C

Solution:

In eukaryotes, DNA is wrapped around positively charged histone octamers to form nucleosomes, which are further organized into chromatin fibers.

Chapter Concept:

Packaging of DNA

It predicts amino acid sequences from mRNA sequences.

It predicts mRNA sequences from amino acid sequences.

It predicts DNA sequences from amino acid sequences.

It predicts protein folding patterns.

Correct Answer: A

Solution:

The codon table is used to predict amino acid sequences from mRNA sequences because the genetic code is degenerate, making reverse prediction ambiguous.

Chapter Concept:

Codon Table and Amino Acid Prediction

DNA polymerase

Helicase

DNA ligase

Primase

Correct Answer: C

Solution:

DNA ligase is the enzyme that joins Okazaki fragments on the lagging strand during DNA replication.

Chapter Concept:

DNA Structure and Replication

Coding strand

Template strand

Leading strand

Lagging strand

Correct Answer: B

Solution:

The template strand of DNA is used as the template for RNA synthesis, while the coding strand has the same sequence as the RNA (except thymine is replaced by uracil).

Chapter Concept:

RNA and Transcription

mRNA

tRNA

rRNA

snRNA

Correct Answer: B

Solution:

tRNA (transfer RNA) is responsible for bringing amino acids to the ribosome and reading the genetic code during protein synthesis.

Chapter Concept:

Types of RNA

The lac operon is activated by glucose.

The lac operon is repressed by lactose.

The lac operon is induced by lactose in the absence of glucose.

The lac operon is always active, regardless of environmental conditions.

Correct Answer: C

Solution:

The lac operon is induced by lactose when glucose is not present, allowing for the metabolism of lactose.

Chapter Concept:

DNA Structure and Replication

The biochemical nature of the genetic material was identified as DNA.

The transforming principle was shown to be a protein.

A non-living substance from the heat-killed S strain could genetically transform the R strain.

The R strain bacteria inherently possess the ability to synthesize a polysaccharide coat.

Correct Answer: C

Solution:

Griffith's experiment demonstrated that a non-living substance from the heat-killed S strain could transform the live R strain into a virulent form, suggesting the presence of a 'transforming principle'. However, the biochemical nature of this principle was not identified in his experiment.

Chapter Concept:

DNA as Genetic Material: Griffith Experiment

Introns are sequences that are translated into proteins.

Introns are sequences that are removed from pre-mRNA during splicing.

Introns are sequences that appear in mature mRNA.

Introns are sequences that code for tRNA molecules.

Correct Answer: B

Solution:

Introns are non-coding sequences that are removed from pre-mRNA during the process of splicing, allowing exons to be joined together to form mature mRNA.

Chapter Concept:

Exons, Introns and Split Genes

The coding strand, because it has the same sequence as the RNA.

The template strand, because it is complementary to the RNA sequence.

Both strands, because they both contain genetic information.

Neither strand, because RNA is synthesized independently.

Correct Answer: B

Solution:

The template strand is used during transcription because it is complementary to the RNA sequence, allowing RNA polymerase to synthesize RNA that is a copy of the coding strand, except that uracil replaces thymine.

Chapter Concept:

Template Strand and Coding Strand

RNA polymerase I

RNA polymerase II

RNA polymerase III

RNA polymerase IV

Correct Answer: C

Solution:

RNA polymerase III is responsible for transcribing tRNA, 5S rRNA, and snRNA in eukaryotic cells.

Chapter Concept:

Eukaryotic RNA Polymerases

16S rRNA

23S rRNA

5S rRNA

18S rRNA

Correct Answer: B

Solution:

In bacteria, the 23S rRNA acts as a ribozyme and catalyzes peptide bond formation during protein synthesis.

Chapter Concept:

Ribosome and Peptide Bond Formation

16S rRNA

5S rRNA

23S rRNA

18S rRNA

Correct Answer: C

Solution:

In bacteria, the 23S rRNA of the large ribosomal subunit acts as a ribozyme, facilitating the formation of peptide bonds during translation.

Chapter Concept:

Ribosome and Peptide Bond Formation

0.34 nm

3.4 nm

1 nm

0.1 nm

Correct Answer: A

Solution:

The distance between two consecutive base pairs in the DNA double helix is approximately 0.34 nm.

Chapter Concept:

Salient Features of DNA Double Helix

The DNA polymerase will correct the mismatch automatically.

The mutation will lead to a frameshift mutation.

The DNA structure will become unstable due to improper hydrogen bonding.

The mutation will have no effect on DNA replication.

Correct Answer: C

Solution:

Adenine normally pairs with Thymine via two hydrogen bonds, and Guanine pairs with Cytosine via three hydrogen bonds. If adenine pairs with cytosine, the hydrogen bonding pattern is disrupted, leading to instability in the DNA structure.

Chapter Concept:

Purines, Pyrimidines and Base Pairing

Sigma factor

Rho factor

RNA polymerase

DNA ligase

Correct Answer: B

Solution:

The rho factor is responsible for the termination of transcription in bacterial transcription.

Chapter Concept:

Bacterial Transcription

All DNA was heavy

All DNA was light

DNA was a hybrid of heavy and light

No DNA was present

Correct Answer: C

Solution:

After one generation in

^{14}N

, the DNA was a hybrid of

^{15}N

and

^{14}N

, demonstrating semiconservative replication.

Chapter Concept:

DNA Structure and Replication

z gene

y gene

a gene

i gene

Correct Answer: A

Solution:

The z gene in the lac operon codes for beta-galactosidase, which is responsible for the hydrolysis of lactose into galactose and glucose.

Chapter Concept:

Lac Operon Structural Genes

RNA polymerase I

RNA polymerase II

RNA polymerase III

RNA polymerase IV

Correct Answer: C

Solution:

RNA polymerase III transcribes tRNA, 5S rRNA, and snRNA in eukaryotic cells.

Chapter Concept:

Eukaryotic RNA Polymerases

Lactose acts as a repressor, preventing transcription.

Lactose binds to the repressor, inactivating it and allowing transcription.

Lactose binds directly to the promoter to initiate transcription.

Lactose is converted to glucose, which then acts as an inducer.

Correct Answer: B

Solution:

Lactose acts as an inducer by binding to the repressor, inactivating it, and allowing RNA polymerase to access the promoter for transcription.

Chapter Concept:

Gene Regulation and Lac Operon

It codes for beta-galactosidase.

It codes for permease.

It codes for transacetylase.

It codes for the repressor protein.

Correct Answer: D

Solution:

The 'i' gene in the lac operon codes for the repressor protein, which binds to the operator region and prevents RNA polymerase from transcribing the operon in the absence of an inducer.

Chapter Concept:

Operon Concept

VNTRs are used to determine the sequence of amino acids in proteins.

VNTRs provide unique patterns that can be used for individual identification in forensic analysis.

VNTRs are responsible for the replication of DNA during cell division.

VNTRs are sequences that code for the production of enzymes in metabolic pathways.

Correct Answer: B

Solution:

VNTRs are polymorphic repetitive DNA sequences that vary in length between individuals, providing unique patterns useful for forensic identification, paternity testing, and population diversity studies.

Chapter Concept:

DNA Fingerprinting

Leading strand synthesis is discontinuous while lagging strand synthesis is continuous.

Leading strand synthesis occurs in the 3' to 5' direction, while lagging strand synthesis occurs in the 5' to 3' direction.

Leading strand synthesis is continuous, while lagging strand synthesis is discontinuous and involves Okazaki fragments.

Both strands are synthesized continuously without any fragments.

Correct Answer: C

Solution:

The leading strand is synthesized continuously in the 5' to 3' direction, while the lagging strand is synthesized discontinuously in short segments known as Okazaki fragments, which are later joined by DNA ligase.

Chapter Concept:

Leading and Lagging Strand Synthesis

The protein will be synthesized normally.

The protein synthesis will not initiate.

A different protein will be synthesized starting from AUA.

The protein will be synthesized but with an incorrect amino acid sequence.

Correct Answer: B

Solution:

The start codon AUG is crucial for the initiation of protein synthesis. Changing it to AUA, which codes for isoleucine, will prevent the ribosome from initiating translation, leading to no protein synthesis.

Chapter Concept:

Genetic Code Features

Hydrogen bond

Ionic bond

3'-5' phosphodiester bond

Peptide bond

Correct Answer: C

Solution:

Nucleotides in a polynucleotide chain are connected through 3'-5' phosphodiester bonds, which link the 3' hydroxyl group of one nucleotide to the 5' phosphate group of the next.

Chapter Concept:

Polynucleotide Chain Structure

The repressor binds to the operator region and prevents transcription.

The repressor is inactivated, allowing RNA polymerase to transcribe the operon.

The operon is permanently turned off.

Glucose is used as the primary energy source, and the operon is not expressed.

Correct Answer: B

Solution:

In the presence of lactose, the repressor is inactivated by the inducer (lactose), allowing RNA polymerase to access the promoter and transcribe the operon.

Chapter Concept:

Gene Regulation and Lac Operon

RNA polymerase

DNA-dependent DNA polymerase

DNA ligase

Helicase

Correct Answer: B

Solution:

DNA-dependent DNA polymerase is the enzyme that catalyzes the polymerization of deoxynucleotides using a DNA template during replication.

Chapter Concept:

Replication Fork and DNA Polymerase

i gene

z gene

y gene

a gene

Correct Answer: B

Solution:

The z gene codes for beta-galactosidase, which is responsible for the hydrolysis of lactose into glucose and galactose.

Chapter Concept:

Gene Regulation and Lac Operon

Protease

RNase

DNase

Lipase

Correct Answer: C

Solution:

The Avery-MacLeod-McCarty experiment demonstrated that DNase inhibited the transformation of R cells into S cells, indicating that DNA was the transforming principle.

Chapter Concept:

Avery-MacLeod-McCarty Experiment

Heavy

Light

Hybrid

None of the above

Correct Answer: C

Solution:

After one generation, the DNA showed an intermediate or hybrid density due to semiconservative replication.

Chapter Concept:

DNA Structure and Replication

Coding strand, 5' to 3' polarity

Template strand, 3' to 5' polarity

Coding strand, 3' to 5' polarity

Template strand, 5' to 3' polarity

Correct Answer: B

Solution:

The template strand is used during transcription and has a 3' to 5' polarity, which allows RNA polymerase to synthesize RNA in the 5' to 3' direction.

Chapter Concept:

Template Strand and Coding Strand

Using both strands would result in identical RNA molecules.

Using both strands would produce complementary RNA molecules, complicating protein synthesis.

Both strands are used, but only one is functional.

Only one strand contains the coding sequence.

Correct Answer: B

Solution:

If both strands were used as templates, they would produce complementary RNA molecules, which could pair and form double-stranded RNA, preventing translation.

Chapter Concept:

RNA and Transcription

Promoter

Structural gene

Terminator

Coding strand

Correct Answer: A

Solution:

The promoter is the DNA sequence that provides the binding site for RNA polymerase and helps define the coding/template strands.

Chapter Concept:

Transcription Unit

Adenine and Thymine

Guanine and Cytosine

Adenine and Uracil

Cytosine and Thymine

Correct Answer: B

Solution:

Guanine pairs with Cytosine by forming three hydrogen bonds, whereas Adenine pairs with Thymine by forming two hydrogen bonds.

Chapter Concept:

Purines, Pyrimidines and Base Pairing

The mice lived, as the R strain is non-virulent.

The mice died, indicating transformation of R strain by the S strain.

The mice lived, as the heat-killed S strain cannot cause disease.

The mice showed no reaction, as both strains were inactive.

Correct Answer: B

Solution:

Griffith's experiment demonstrated that the heat-killed S strain could transform the live R strain into a virulent form, causing the mice to die.

Chapter Concept:

DNA as Genetic Material: Griffith Experiment

3.4 nm

2.0 nm

5.0 nm

1.0 nm

Correct Answer: A

Solution:

The pitch of the DNA double helix is 3.4 nm, which is the distance covered by one complete turn of the helix.

Chapter Concept:

Salient Features of DNA Double Helix

Codes for beta-galactosidase, which hydrolyzes lactose into glucose and galactose.

Codes for permease, which increases cell permeability to lactose.

Codes for transacetylase, which transfers acetyl groups.

Acts as a repressor to inhibit the operon.

Correct Answer: A

Solution:

The 'z' gene in the lac operon codes for beta-galactosidase, an enzyme that hydrolyzes lactose into glucose and galactose, facilitating lactose metabolism.

Chapter Concept:

Lac Operon Structural Genes

DNA replication is conservative.

DNA replication is semiconservative.

DNA replication is dispersive.

DNA replication is non-conservative.

Correct Answer: B

Solution:

The Meselson-Stahl experiment demonstrated that DNA replication is semiconservative, meaning each daughter DNA molecule consists of one parental and one newly synthesized strand.

Chapter Concept:

Meselson-Stahl Experiment

20%

30%

40%

60%

Correct Answer: A

Solution:

Chargaff's Rule states that in double-stranded DNA, the amount of adenine (A) equals thymine (T) and the amount of guanine (G) equals cytosine (C). If adenine is 30%, then thymine is also 30%. This leaves 40% for guanine and cytosine combined, hence guanine would be 20%.

Chapter Concept:

Chargaff’s Rule

AUG is a stop codon that terminates translation.

AUG is a start codon that initiates translation and codes for Methionine.

AUG is a codon that codes for the amino acid Lysine.

AUG is a universal stop codon in all organisms.

Correct Answer: B

Solution:

AUG serves as the start codon in mRNA, initiating translation and coding for the amino acid Methionine.

Chapter Concept:

Genetic Code and Translation

Genetic material in some viruses

Adapter molecule in protein synthesis

Main storage form of genetic information in eukaryotes

Catalytic molecule in some biochemical reactions

Correct Answer: C

Solution:

RNA is primarily involved in protein synthesis and can act as a genetic material in some viruses, but DNA is the main storage form of genetic information in eukaryotes.

Chapter Concept:

RNA and Transcription

Point mutation

Insertion mutation

Deletion mutation

Frameshift mutation

Correct Answer: A

Solution:

Sickle-cell anemia is caused by a point mutation in the gene for the beta-globin chain, where a single base pair change results in the substitution of glutamate with valine.

Chapter Concept:

Mutations and Genetic Code

The sugar-phosphate backbone

Antiparallel strands

Complementary base pairing with purines pairing with pyrimidines

Right-handed coiling

Correct Answer: C

Solution:

The uniform diameter of the DNA double helix is due to complementary base pairing, where a purine pairs with a pyrimidine, maintaining a consistent distance between the two strands.

Chapter Concept:

Salient Features of DNA Double Helix

tRNA has an anticodon loop complementary to the codon on mRNA.

tRNA binds to stop codons to terminate translation.

tRNA is not involved in the process of translation.

tRNA does not have an amino acid acceptor end.

Correct Answer: A

Solution:

tRNA acts as an adapter molecule with an anticodon loop that is complementary to the codon on mRNA and an amino acid acceptor end. There are no tRNAs for stop codons.

Chapter Concept:

tRNA as Adapter Molecule

DNA \rightarrow RNA \rightarrow Protein

RNA \rightarrow DNA \rightarrow Protein

Protein \rightarrow RNA \rightarrow DNA

DNA \rightarrow Protein \rightarrow RNA

Correct Answer: A

Solution:

The Central Dogma of Molecular Biology describes the flow of genetic information from DNA to RNA to Protein.

Chapter Concept:

Central Dogma of Molecular Biology

tRNA acts as a template for the synthesis of proteins.

tRNA carries amino acids to the ribosome and matches them with the mRNA codons using its anticodon loop.

tRNA is responsible for the replication of DNA.

tRNA catalyzes the formation of peptide bonds between amino acids.

Correct Answer: B

Solution:

tRNA functions as an adapter molecule by carrying specific amino acids to the ribosome and matching them with the corresponding codons on the mRNA through its anticodon loop.

Chapter Concept:

tRNA as Adapter Molecule

Radioactive sulfur (

^{35}S

)

Radioactive phosphorus (

^{32}P

)

Radioactive carbon (

^{14}C

)

Radioactive nitrogen (

^{15}N

)

Correct Answer: B

Solution:

Radioactive phosphorus (

^{32}P

) was used to label the DNA because DNA contains phosphorus but not sulfur.

Chapter Concept:

Hershey-Chase Experiment

mRNA

tRNA

rRNA

snRNA

Correct Answer: B

Solution:

tRNA (transfer RNA) is responsible for bringing amino acids to the ribosome and reading the codons on the mRNA during protein synthesis.

Chapter Concept:

Types of RNA

DNA helicase, 3' to 5'

DNA ligase, 5' to 3'

DNA-dependent DNA polymerase, 5' to 3'

RNA polymerase, 3' to 5'

Correct Answer: C

Solution:

DNA-dependent DNA polymerase synthesizes the new DNA strand in the 5' to 3' direction using the template strand.

Chapter Concept:

Replication Fork and DNA Polymerase

Forensic identification

Genetic modification

Protein synthesis

Photosynthesis

Correct Answer: A

Solution:

DNA fingerprinting is primarily used for forensic identification, paternity testing, and population diversity studies by comparing DNA sequences using polymorphic repetitive DNA, especially VNTRs.

Chapter Concept:

DNA Fingerprinting

Universality

Degeneracy

Non-overlapping

Triplet nature

Correct Answer: B

Solution:

The genetic code is described as 'degenerate' because several codons can specify the same amino acid. This feature allows for some redundancy in the genetic code.

Chapter Concept:

Genetic Code Features

The inducer binds to the promoter, facilitating RNA polymerase binding.

The inducer inactivates the repressor, allowing transcription to proceed.

The inducer binds directly to the operator, blocking the repressor.

The inducer enhances the binding of the repressor to the operator.

Correct Answer: B

Solution:

The inducer, such as lactose, binds to the repressor protein, inactivating it. This prevents the repressor from binding to the operator, thereby allowing RNA polymerase to access the promoter and initiate transcription of the operon.

Chapter Concept:

Operon Concept

It catalyzes the formation of peptide bonds.

It facilitates the binding of RNA polymerase to the promoter.

It terminates the transcription process.

It is responsible for the splicing of introns.

Correct Answer: B

Solution:

The sigma factor is part of the RNA polymerase complex that recognizes the promoter and facilitates the binding of RNA polymerase to the DNA to initiate transcription.

Chapter Concept:

RNA and Transcription

True or False

Correct Answer: True

Solution:

The DNA double helix structure consists of two antiparallel polynucleotide chains where the sugar-phosphate backbone is on the outside and the nitrogenous bases are on the inside, forming base pairs.

Chapter Concept :

Salient Features of DNA Double Helix

Correct Answer: True

Solution:

The semiconservative model of DNA replication was demonstrated by the Meselson-Stahl experiment, showing that each daughter DNA molecule consists of one original strand and one new strand.

Chapter Concept :

DNA Structure and Replication

Correct Answer: True

Solution:

The semiconservative model of DNA replication was confirmed by the Meselson-Stahl experiment, showing that each daughter DNA molecule consists of one strand from the parent and one newly synthesized strand.

Chapter Concept :

DNA Structure and Replication

Correct Answer: False

Solution:

Griffith's experiment demonstrated the existence of a 'transforming principle' but did not identify DNA as its biochemical nature. It was later work by Avery, MacLeod, and McCarty that identified DNA as the transforming principle.

Chapter Concept :

DNA as Genetic Material: Griffith Experiment

Correct Answer: True

Solution:

DNA's stability is attributed to the presence of thymine, which replaces uracil found in RNA, and the absence of the reactive 2'-OH group that makes RNA more labile.

Chapter Concept :

Properties of Genetic Material

Correct Answer: True

Solution:

Lactose acts as an inducer by binding to the repressor, changing its shape, and preventing it from binding to the operator. This allows RNA polymerase to access the promoter and transcribe the operon.

Chapter Concept :

Gene Regulation and Lac Operon

Correct Answer: False

Solution:

In the Hershey-Chase experiment, radioactive phosphorus was used to label the DNA, while radioactive sulfur was used to label the protein of bacteriophages.

Chapter Concept :

Hershey-Chase Experiment

Correct Answer: True

Solution:

The Avery-MacLeod-McCarty experiment showed that DNA from heat-killed S cells could transform R cells. Proteases and RNases did not stop the transformation, but DNase did, indicating that DNA is the transforming principle.

Chapter Concept :

Avery-MacLeod-McCarty Experiment

Correct Answer: True

Solution:

In the DNA double helix, adenine forms two hydrogen bonds with thymine, which is a key feature of base pairing.

Chapter Concept :

Purines, Pyrimidines and Base Pairing

Correct Answer: True

Solution:

In eukaryotic cells, DNA is wrapped around histone proteins to form nucleosomes, which are the basic units of chromatin structure.

Chapter Concept :

Packaging of DNA

Correct Answer: True

Solution:

The genetic code is indeed a triplet code, as proposed by George Gamow, where each amino acid is coded by a combination of three nucleotides, allowing for 64 possible codons.

Chapter Concept :

Genetic Code and Translation

Correct Answer: True

Solution:

Chargaff's Rule states that in double-stranded DNA, the number of adenine bases equals the number of thymine bases and the number of guanine bases equals the number of cytosine bases. This purine-pyrimidine pairing keeps the DNA helix width nearly constant.

Chapter Concept :

Chargaff’s Rule

Correct Answer: True

Solution:

Sickle cell anemia is caused by a point mutation in the beta globin gene, where a single base pair change results in the substitution of glutamate with valine.

Chapter Concept :

Mutations and Genetic Code

Correct Answer: True

Solution:

Chargaff's Rule states that in double-stranded DNA, adenine pairs with thymine, and guanine pairs with cytosine, resulting in equal amounts of adenine and thymine.

Chapter Concept :

Chargaff’s Rule

Correct Answer: True

Solution:

The genetic code is nearly universal across all organisms, with very few exceptions such as mitochondrial codons and some protozoans.

Chapter Concept :

Genetic Code and Translation

Correct Answer: False

Solution:

In transcription, RNA polymerase binds to the promoter region but uses the template strand, not the coding strand, to synthesize RNA.

Chapter Concept :

RNA and Transcription

Correct Answer: True

Solution:

The Central Dogma describes the flow of genetic information in cells from DNA to RNA to protein. However, in some viruses, reverse transcription allows information to flow from RNA back to DNA.

Chapter Concept :

Central Dogma of Molecular Biology

Correct Answer: True

Solution:

Nucleotides in a polynucleotide chain are linked through 3'-5' phosphodiester bonds, which connect the 3' hydroxyl group of one nucleotide's sugar to the 5' phosphate group of the next nucleotide.

Chapter Concept :

Polynucleotide Chain Structure

Correct Answer: True

Solution:

During transcription, only one of the two DNA strands is used as a template to synthesize RNA. This ensures that the RNA sequence is complementary to the DNA template strand.

Chapter Concept :

RNA and Transcription

Correct Answer: True

Solution:

Sickle cell anemia is caused by a point mutation in the beta globin gene, where a single base pair change results in the substitution of glutamate with valine.

Chapter Concept :

Mutations and Genetic Code

Correct Answer: True

Solution:

The DNA double helix, as described by Watson and Crick, consists of two antiparallel polynucleotide chains. The sugar-phosphate backbone is located on the outside, while the nitrogenous bases are on the inside. The helix is right-handed with a pitch of 3.4 nm and roughly 10 base pairs per turn.

Chapter Concept :

Salient Features of DNA Double Helix

Correct Answer: False

Solution:

Adenine pairs with thymine through two hydrogen bonds, not three.

Chapter Concept :

Purines, Pyrimidines and Base Pairing

Correct Answer: True

Solution:

In eukaryotes, DNA is organized into nucleosomes, where the negatively charged DNA is wrapped around positively charged histone octamers. This structure is essential for DNA packaging and regulation.

Chapter Concept :

Packaging of DNA

Correct Answer: True

Solution:

Nucleotides in a polynucleotide chain are linked through 3'-5' phosphodiester bonds, which connect the 3' hydroxyl group of one nucleotide to the 5' phosphate group of the next.

Chapter Concept :

Polynucleotide Chain Structure

Correct Answer: False

Solution:

The i gene codes for the repressor of the lac operon, not the inducer. The inducer, such as lactose, inactivates the repressor, allowing transcription to proceed.

Chapter Concept :

Gene Regulation and Lac Operon

Molecular Basis of Inheri..

Learning Objectives

Revision Notes & Summary

Molecular Basis of Inheritance

Exercises

Exam Tips & Common Mistakes

Common Mistakes and Exam Tips

Common Pitfalls

Exam Tips

AI Learning Assistant

Practice Test – MCQs, True/False

Experience the StudyTunnel Method

Step 1: Chapter Practice

Step 2: Term Boss Exam

Step 3: Redemption Arena

Practice, Analyze & Improve 🚀

Multiple Choice Questions

Q1.A mutation in the 23S rRNA of a bacterial ribosome impairs its ability to catalyze peptide bond formation. What is the most likely consequence of this mutation?

Correct Answer: C

Q2.In a transcription unit, what would happen if the promoter sequence is switched with the terminator sequence?

Correct Answer: B

Q3.Which experimental evidence first demonstrated the semiconservative nature of DNA replication?

Correct Answer: D

Q4.Which of the following statements correctly explains why DNA is more stable than RNA as a genetic material?

Correct Answer: A

Q5.Which of the following statements correctly explains why reverse prediction of amino acids from a given protein sequence is ambiguous?

Correct Answer: A

Q6.Which of the following properties is NOT essential for a molecule to function as genetic material?

Correct Answer: D

Q7.In the process of translation, what role does tRNA play?

Correct Answer: C

Q8.Which of the following is a feature of the genetic code?

Correct Answer: A

Q9.How does a frameshift mutation affect protein synthesis?

Correct Answer: B

Q10.Which component of the lac operon is responsible for coding the enzyme that hydrolyzes lactose into glucose and galactose?

Correct Answer: B

Q11.In a hypothetical scenario, a frameshift mutation occurs in a gene sequence. Which of the following changes would most likely result from this mutation?

Correct Answer: A

Q12.Which type of mutation is responsible for sickle-cell anemia, and what is the specific change in the amino acid sequence?

Correct Answer: A

Q13.What is the approximate number of base pairs in the human genome?

Correct Answer: B

Q14.In the context of the human genome, which of the following features is NOT true?

Correct Answer: D

Q15.How did the Avery-MacLeod-McCarty experiment contribute to the understanding of genetic material?

Correct Answer: C

Q16.Given the mRNA sequence 5'-AUG UUU UUC UUC UUU UUU UUC-3', predict the sequence of amino acids that it codes for using the genetic code table.

Correct Answer: A

Q17.Consider the mRNA sequence: 5'-AUG UUU UUC UUC UUU UUU UUC-3'. What is the sequence of amino acids coded by this mRNA?

Correct Answer: A

Q18.Which of the following statements about the genetic code is true?

Correct Answer: A

Q19.During the process of transcription, why is only one strand of the DNA used as a template for RNA synthesis?

Correct Answer: A

Q20.In the context of the Hershey-Chase experiment, which of the following statements is correct?

Correct Answer: C

Q21.What conclusion can be drawn from the Meselson-Stahl experiment regarding the mechanism of DNA replication?

Correct Answer: B

Q22.In the context of genetic material, why is RNA considered more dynamic than DNA?

Correct Answer: B

Q23.Which of the following statements best describes semiconservative replication of DNA?

Correct Answer: B

Q24.In the Hershey-Chase experiment, which radioactive element was used to label the DNA of bacteriophages?

Correct Answer: B

Q25.How does the presence of uracil in RNA instead of thymine in DNA affect the stability of these nucleic acids?

Correct Answer: C

Q26.Which of the following correctly describes the role of the promoter in the transcription unit?

Correct Answer: A

Q27.In the context of the Human Genome Project, what is the primary purpose of using EST-based gene identification?

Correct Answer: B

Q28.In Griffith's experiment with Streptococcus pneumoniae, which combination of bacterial strains led to the death of mice, indicating the presence of a 'transforming principle'?

Correct Answer: A

Q29.A scientist is analyzing a DNA sample and finds that it contains 22% cytosine. According to Chargaff's Rule, what percentage of thymine should be expected in this DNA sample?

Correct Answer: B

Q30.In the context of DNA replication, what is the significance of the antiparallel nature of the DNA strands?

Correct Answer: C

Q31.In the Meselson-Stahl experiment, which type of DNA was observed after one generation of E.coliE. coliE.coli grown in a medium with normal 14NH4Cl^{14}NH_4Cl14NH4​Cl following growth in 15NH4Cl^{15}NH_4Cl15NH4​Cl?

Correct Answer: C

Q32.In the absence of lactose, what role does the repressor protein play in the lac operon?