Biology

DNA and Genetics

1,095 Questions

DNA and genetics questions explore molecular biology, DNA replication, and genetic engineering techniques. These topics are essential for various competitive exams requiring a strong foundation in life sciences. Practice these questions to understand complex biological processes thoroughly.

DNA replication mechanismsGenetic engineering techniquesGene editing toolsPolymerase chain reactionDNA sequencing methods

DNA and Genetics Questions

Multiple choice

Assertion (A): The normal role of restriction endonucleases in bacterial cells is to degrade the bacterial chromosome into small pieces during replication. Reason (R): Bacterial cells protect their own DNA from degradation by restriction endonucleases by deleting all recognition sites from the genome.

Directions: In the following question, there are two statements, Assertion (A) and Reason (R). Consider both the statements independently and mark your answer as under:

1. A and R both are correct and R is the correct explanation of A.
2. A and R both are correct and R is not the correct explanation of A.
3. A is correct and R is incorrect.
4. A is incorrect and R is correct.
5. A and R both are incorrect.

  1. (1)

  2. (2)

  3. (3)

  4. (4)

  5. (5)
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This option is correct because the normal role of restriction endonucleases in bacterial cells is to degrade invading phage DNA. Bacterial cells protect their own DNA from degradation by restriction endonucleases by methylating the DNA at the sites that the enzyme recognises.  

Multiple choice

Which of the following is a pair of homologous recombination methods?

  1. DNA shuffling and Genome shuffling

  2. Exon shuffling and ITCHY

  3. DNA shuffling and Exon shuffling

  4. Genome shuffling and Exon shuffling

  5. Genome shuffling and ITCHY
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This option is correct because DNA shuffling and Genome shuffling are homologous recombination methods.

Multiple choice

Which of the following statements are false?

  1. Transposition occurs by non-replicative mechanism only.
  2. Homologous recombination between multiple copies of a transposon causes rearrangement of host DNA.
  3. Homologous recombination between the repeats of transposons may lead to precise or imprecise excision.
  4. Imprecise excision describes the removal of a transposon plus one of the duplicated target sequences from the chromosome.

  1. 1 and 2

  2. 1 and 3

  3. 1 and 4

  4. 2 and 3

  5. 3 and 4
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Correct answer. Transposition occurs by both replicative and non-replicative mechanisms. All transposons use a common mechanism in which staggered nicks are made in target DNA, the transposon is joined to the protruding ends, and the gaps are filled. The order of events and exact nature of the connections between transposon and target DNA determine whether transposition is replicative or nonreplicative. Precise excision describes the removal of a transposon plus one of the duplicated target sequences from the chromosome. Imprecise excision occurs when the transposon removes itself from the original insertion site, but leaves behind some of its sequence.

Multiple choice

Assertion (A): Transposition starts by forming a strand transfer complex in which the transposon is connected to the target site through one strand at each end. Reason (R): Replicative transposition proceeds through a cointegrate.

Directions: In the following question, there are two statements, Assertion (A) and Reason (R). Consider both the statements independently and mark your answer as follows:

1. A and R both are correct and R is the correct explanation of A.
2. A and R both are correct and R is not the correct explanation of A.
3. A is correct and R is incorrect.
4. A is incorrect and R is correct.
5. A and R both are incorrect.

  1. (1)

  2. (2)

  3. (3)

  4. (4)

  5. (5)
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Correct answer. Transposition starts by forming a strand transfer complex in which the transposon is connected to the target site through one strand at each end. Replicative transposition proceeds through a cointegrate. Replication of a strand transfer complex generates a cointegrate, which is a fusion of the donor and target replicons. The cointegrate has two copies of the transposon, which lie between the original replicons. Recombination between the transposon copies regenerates the original replicons, but the recipient has gained a copy of the transposon.

Multiple choice

Which of the following are examples of random mutagenesis strategies?

P. DOGS Q. StEP R. SeSAM S. Error-prone PCR

  1. P and Q

  2. P and R

  3. Q and R

  4. Q and S

  5. R and S
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This option is correct because SeSaM and Error prone PCR are examples of random mutagenesis strategies. Sequence saturation mutagenesis (SeSaM) is a conceptually novel and practically simple method that truly randomizes a target sequence at every single nucleotide position and Error prone PCR is a method by which random mutants may be inserted into any piece of DNA.

Multiple choice

Assertion: Gene recombination refers to the exchange of blocks of genetic material among two or more DNA strands. Reason: In site-specific recombination, specialized nucleotide sequences exhibiting some degree of target site specificity are moved between homologous sites within a genome.

Directions: In the following question, there are two statements, Assertion (A) and Reason (R). Consider both the statements independently and mark your answer as follows:

1. A and R both are correct and R is the correct explanation of A.
2. A and R both are correct and R is not the correct explanation of A.
3. A is correct and R is incorrect.
4. A is incorrect and R is correct.
5. A and R both are incorrect.

  1. (1)

  2. (2)

  3. (3)

  4. (4)

  5. (5)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Correct answer. Gene recombination refers to the exchange of blocks of genetic material among two or more DNA strands. In site-specific recombination, specialized nucleotide sequences exhibiting some degree of target site specificity are moved between nonhomologous sites within a genome.

Multiple choice

The transposons cannot exist independent of a replicon. Which of the following may be the reason for that?

  1. As they have inverted repeats.

  2. As they have transposase gene.

  3. As they have antibiotic resistance gene.

  4. As they can ligate transposon into a target.

  5. As they do not have an ori of their own.

Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Transposons are mobile segments of DNA that cannot exist independent of a replicon because they don't have an ori of their own. Transposons do not contain their own origin of replication, but rely on the host DNA to provide this feature. Each replicon contains an origin for initiation of replication. 

Multiple choice

For creating a recombinant DNA molecule, which enzyme should be used to cut open the target gene and the carrier plasmid?

  1. DNAse for target gene and restriction endonuclease for plasmid

  2. DNAse for plasmid and restriction endonuclease for target gene

  3. DNAse for cutting both target gene and plasmid

  4. Restriction endonuclease for cutting both target gene and plasmid

  5. Restriction exonuclease for cutting both target gene and plasmid
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Cutting both the target gene and the carrier plasmid will create complementary sticky ends required for fitting the target gene into the carrier plasmid.

Multiple choice

The first step in the polymerase chain reaction (PCR) is

  1. denaturation

  2. heating

  3. primer extension

  4. annealing

  5. cooling
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Denaturation or separation of DNA strands is the first step. This step separates the strands by heating to a high temperature. Each separate strand can then serve as a template for copying.

Multiple choice

Different restriction enzymes cut at different places and generate a specific set of DNA lengths. This is called Restriction Fragment Length Polymorphism. This technique is used in

  1. polymerase chain reaction

  2. genetic engineering

  3. DNA fingerprinting

  4. Southern blotting

  5. biotechnology
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

It is a technique for the identification of an organism by matching the DNA restriction fragment lengths by using the technique RFLP. Same DNA will generate same DNA lengths when treated with a fixed set of restriction enzymes.