Biochemistry Multiple Choice Questions on “Nucleic Acid Chemistry”.
1. What happens in hypochromicity?
A. When DNA is in bound form, there is decrease in absorption of UV light
B. When DNA is in bound form, there is increase in absorption of UV light
C. When DNA is in unbound form, it is more stable
D. When DNA is in unbound form, there is decrease in absorption of UV light
Answer: A
Clarification: It describes the decrease in absorbance of UV light in a double stranded DNA.
2. What happens in hyperchromicity?
A. When DNA is in bound form, there is decrease in absorption of UV light
B. When DNA is in bound form, there is increase in absorption of UV light
C. When DNA is in unbound form, it is more stable
D. When DNA is in unbound form, there is increase in absorption of UV light
Answer: D
Clarification: It describes the increase in absorption of UV light in a single stranded DNA.
3. Which of the following is true about tm?
A. It can be termed as renaturation temperature
B. The higher the content of G ≡ C base pairs, the higher the tm
C. The higher the content of A = T base pairs, the higher the tm
D. The higher the content of G ≡ C base pairs, the lower the tm
Answer: B
Clarification: Tm is the melting temperature or denaturation temperature.
4. Which of the following is false?
A. The stability of an RNA-DNA hybrid is generally intermediate between that of RNA and DNA
B. RNA duplexes are more stable than DNA duplexes
C. DNA duplexes are more stable than RNA duplexes
D. DNA duplexes are less stable than RNA- DNA hybrid
Answer: C
Clarification: RNA duplexes are more stable than DNA duplexes.
5. DNA denaturation is measured by absorbance at ___________
A. 220nm
B. 230nm
C. 250nm
D. 260nm
Answer: D
Clarification: At 260nm absorbance, DNA denaturation is measured.
6. Which of the following is false about denaturation?
A. Disruption of hydrogen bonds
B. Disruption of phosphodiester linkage
C. Loss of helical structure of DNA
D. It is resulted as a result of change in pH or increase in temperature
Answer: B
Clarification: Phosphodiester linkages are not broken by denaturation.
7. Which of the following nucleotides is not present in RNA?
A. AMP
B. GMP
C. CMP
D. TMP
Answer: D
Clarification: Thymidine monophosphate is present in DNA.
8. Which of the following nucleotides is not present in DNA?
A. AMP
B. GMP
C. CMP
D. UMP
Answer: D
Clarification: Uridine monophosphate is present in RNA.
9. Which of the following is false?
A. RNA does not obey Chargaff’s rule
B. DNAs can be identified by Orcinol color reaction
C. In RNA OH group is present at 2’ position
D. Alkali hydrolyses RNA to 2’3’-cyclic diesters
Answer: B
Clarification: RNAs can be identified by Orcinol color reaction.
10. Which of the following involves carrying genetic information from DNA for protein synthesis?
A. m-RNA
B. t-RNA
C. r-RNA
D. sn-RNA
Answer: A
Clarification: Messenger RNA carries genetic information from DNA for protein synthesis.
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