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

Which of the following statements is/are correct?

  1. Endogenous antigens are present on the cell surface along with MHC-I.
  2. The RNA primer synthesised during the replication process in bacteria is removed by DNA polymerase II.
  3. Type III restriction endonucleases cut DNA at defined positions close to or within their recognition sequences.

  1. Only 1

  2. Only 2

  3. Only 3

  4. 1 and 2

  5. 2 and 3
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This option is correct because type III restriction endonucleases cut DNA outside of their recognition sequences and require two such sequences in opposite orientations within the same DNA molecule to accomplish cleavage.

Multiple choice

Which of the following statements is incorrect?

  1. Southern blotting technique depends on similarities between the sequences of probe RNA and experimental RNA.

  2. Electroporation is used to transfer polar molecules like DNA into host cells.

  3. Northern blotting is a laboratory method used to detect specific RNA molecules from a mixture of RNA molecules.

  4. Gel electrophoresis is a basic technique used to separate DNA, RNA or proteins.

  5. PCR is a laboratory technique for amplifying a specific DNA sequence.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This option is correct because southern blotting technique is a laboratory method used to detect specific DNA molecules among other DNA molecules.  

Multiple choice

Which of the following statements is false?

  1. The term enzyme was proposed by Kuhne.

  2. The first enzyme molecule to be isolated in pure crystalline form was urease.

  3. Synthesis of enzymes is regulated by inducer and repressor genes.

  4. DNA ligase was first isolated from bacteriophages.

  5. Ribozyme is an RNA with enzyme activity.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This option is correct because synthesis of enzymes is regulated by operator and regulator genes.

Multiple choice

Which of the following statements is not correct?

  1. Plasmids are circular pieces of double-stranded DNA that exist separately from chromosomal DNA.

  2. Plasmids that can be propagated in cells of two or more different species are called expression vectors.

  3. Shuttle vectors can be used in both eukaryotes and prokaryotes.

  4. A cloning vector is a small piece of DNA into which a foreign DNA fragment can be inserted for cloning purposes.

  5. Replacement vector is a cloning vector in which part of the normal genome is replaced by foreign DNA.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This option is correct because plasmids that can be propagated in cells of two or more different species are called shuttle vectors.

Multiple choice

Which of the following matchings is not correct?

  1. Recombinant DNA technology - combining genes from different species

  2. Restriction fragments - pieces of DNA that have been cut into different lengths

  3. Genomic library - all the genes contained in one kind of organism

  4. Restriction enzymes – DNA-cutting enzymes

  5. DNA fingerprinting - technique for identification of patterns that occur in DNA
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This option is correct because a genomic library is a collection of cloned DNA pieces from a genome.

Multiple choice

Directions: Read the given statements and choose the correct option.

Assertion: Zinc-finger nucleases (ZFNs) are artificial restriction enzymes. Reason: The DNA-binding domains of individual ZFNs typically contain between nine and eighteen individual zinc finger repeats.

  1. A and R are both correct and R is the correct explanation of A.

  2. A and R are both 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 are both incorrect.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This option is correct.

Multiple choice

The technique known as Gel electrophoresis used to analyse DNA molecule involves __________.

  1. synthesis of new DNA strands from subunits

  2. removal of defective genes from DNA

  3. production of genetically engineered DNA molecules

  4. separation of DNA fragments on the basis of size

  5. replication of DNA fragments
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Gel electrophoresis is a laboratory technique used to separate DNA fragments as per their size through the gel matrix using electricity. The DNA fragments are attracted towards the other end of the matrix, and the smaller molecules move faster than the large ones. This technique is used in DNA profiling to know possible genetic relationships of organisms.

Multiple choice

In nature, Agrobacterium tumefaciens mediated infection of plant cells leads to P. crown gall disease in plants Q. hairy root disease in plants R. transfer of T-DNA into the plant chromosome S. transfer of Ri-plasmid into the plant cell

  1. S only

  2. P and R only

  3. Q and S only

  4. Q only
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Agrobacterium tumefaciens causes crown gall disease (P) through transfer of T-DNA (tumor-DNA) from its Ti (tumor-inducing) plasmid into the plant chromosome (R). The T-DNA becomes integrated into the plant genome and causes tumor formation. Hairy root disease (Q) and Ri-plasmid transfer (S) are caused by Agrobacterium rhizogenes, not A. tumefaciens. Therefore, only P and R are correct for A. tumefaciens, making option B the right answer. Option A incorrectly selects S (which relates to A. rhizogenes), option C incorrectly includes Q and S (both A. rhizogenes features), and option D is incomplete.

Multiple choice

HAT (hypoxanthine, aminopterin and thymidine) is used for selecting the hybridomas based on the following I. Only hybridoma will grow since it inherited the HGPRT genes from B-cells and can synthesize DNA from hypoxanthine. II. Myeloma cells will not grow in cultures since de novo synthesis is blocked by aminopterin and due to the lack of HGPRT enzyme.

  1. only I is true

  2. only II is true

  3. both I and II are true

  4. I is true and II is false
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

HAT medium selection works through two complementary mechanisms. Statement I is correct: hybridomas inherit HGPRT (hypoxanthine-guanine phosphoribosyltransferase) from B-cells, enabling them to use hypoxanthine for nucleotide synthesis when de novo pathway is blocked. Statement II is correct: myeloma cells are HGPRT-deficient, so when aminopterin blocks de novo synthesis, they cannot synthesize DNA and die. The combination selects for only hybridomas (B-cell + myeloma fusion) that survive because they have immortality from myeloma and HGPRT from B-cells. Therefore, option C (both I and II are true) is correct.

Multiple choice

Which of the following does not code by pol gene?

  1. Proteases

  2. Reverse transcriptase

  3. Integrase

  4. RNA polymerase
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This enzyme is involved in the production of RNA from DNA through transcription. It adds ribonucleotides to growing RNA transcripts at the 3' end. The pol gene does not encode for RNA polymerase.