SBA — Single Best Answer · Review
Question 578
Genetics → General
Classification
Question
SSBAOptions
Explanation
Complementary DNA strands are held together by hydrogen bonding between their bases. Disrupting these interactions can separate the strands without cutting their sugar–phosphate backbones, consistent with preservation of each strand's length and sequence. Thermal denaturation separates the duplex; helicases also enable strand separation. Neither process requires conversion of DNA into RNA.
Option Validity
A) Extensive cleavage of the backbone would fragment the strands, contrary to their preserved individual lengths.
C) Ribose is the RNA sugar. Replacing the DNA sugar is not the mechanism of separating two intact DNA strands.
D) Uracil replaces thymine in the usual RNA base set, but changing the base set would not account for two DNA strands retaining their original sequences.
E) RNA polymerase produces an RNA copy during transcription. Production of new RNA does not explain the observed separation of the original intact DNA strands by heating.
Further Reading
Saxena R. Textbook for MRCOG-1: Basic Sciences in Obstetrics and Gynaecology. 1st ed. Jaypee Brothers Medical Publishers; 2016. Chapter 8: Genetics — Deoxyribonucleic Acid; Process of Protein Synthesis — Transcription. Printed pages 254–255.