300+ TOP DNA STRUCTURE Objective Questions and Answers

DNA STRUCTURE Multiple Choice Questions :-

1. The accepted hypothesis for DNA replication is

A. conservative theory
B. dispersive theory
C. semi-conservative theory
D. evolutionary theory

Answer: C

2. When DNA polymerase is in contact with guanine in the parental strand, what does it add to the growing daughter strand?

A. Phosphate
B. Cytosine
C. Uracil
D. Guanine

Answer: B

3. Telomeres are usually rich in which nucleotide?

A. Adenine
B. Guanine
C. Thymine
D. Cytosine

Answer: B

4. Which is the largest among the followings?

A. Nucleotide
B. Nitrogenous base
C. Phosphate
D. Carbon

Answer: A

5. The chromosomal DNA complexes with

A. three types of histone as H1, H2A and H4
B. five types of histone as H1, H2A, H2B, H3 and H4
C. four types of histone as H1, H2A, H3 and H4
D. two types of histone as H1 and H4

Answer: B

6. Taylor, Woods and Hughes labeled Vicia DNA by allowing new DNA synthesis in the presence of radioactive thymine. After DNA replication (S phase of the cell cycle), it was observed that

A. only one chromatid of a chromosome was labeled
B. both chromatids of a chromosome were labeled
C. both (a) and (b)
D. neither chromatid was labeled

Answer: B

7. In DNA double helix, the two DNA chains are held together by

A. covalent bonds between the pair of bases
B. hydrogen bonds between the pair of bases
C. ionic bonds between the pair of bases
D. none of the above

Answer: B

8. The 5′ and 3′ numbers are related to the

A. length of the DNA strand
B. carbon number in sugar
C. the number of phosphates
D. the base pair rule

Answer: B

9. Messelsen and Stahl model of replication was called

A. conservative replication
B. semi-conservative replication
C. dispersive replication
D. Cri du Chat

Answer: B

10. The most common liquid volumes in molecular biology are measured in

A. ml
B. µl
C. nl
D. 1

Answer: B

DNA STRUCTURE Objective type Questions with Answers

11. DNA replication takes place in which direction?

A. 3′ to 5′
B. 5 ‘to 3’
C. Randomly
D. Vary from organism to organism

Answer: B

12. DNA gyrase in E. coli

A. adds positive supercoils to chromosomal DNA
B. can be inhibited with antibiotics
C. is required only at the oriC site
D. performs the same function as helicase in eukaryotes

Answer: B

13. In DNA, there are

A. five bases known as adenine, guanine, thymine, tryptophan and cytosine
B. four bases known as adenine, guanine, thymine and cytosine
C. three bases known as adenine, guanine and cytosine
D. only two bases known as adenine and cytosine

Answer: B

14. In DNA, guanine pairs with

A. Adenine B. Cytosine
C. Thymine D. Uracil

Answer: B

15. Which of the following is incorrect?

A. In DNA double helix, two strands of the DNA are bound with each other with the bases
B. Adenine always pairs with thymine
C. Guanine always pairs with the cytosine
D. None of the above

Answer: D

16. What is the only common methylation in the DNA of eukaryotes?

A. Adenosine in GpA dinucleotides
B. Guanosine in ApGpA trinucleotides
C. Cytosine in CpG dinucleotides
D. None of the above

Answer: C

17. DNAs when charged, migrate in a gel towards the

A. positive pole
B. negative pole
C. will not migrate
D. none of these

Answer: A

18. What is the approximate size (in kb) of the E. coli genome?

A. 3000 kilobase
B. 4500 kilobase
C. 5500 kilobase
D. 6500 kilobase

Answer: B

19. In the study of one experiment it was found that the value of Tm for DNA is = 40° C. If the cell has 20% GC at the above Tm, then what will be value of ‘Tm’ if the GC% increases to 60%?

A. Remains same
B. Increases
C. Decreases
D. Can not be compared

Answer: B

20. What is the range of melting point temperatures (Tm) for most DNA molecules?

A. 50 to 60°C
B. 60 to 80°C
C. 70 to 90°C
D. 80 to l00°C

Answer: D

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