Question

Two students are given two different double -stranded DNA molecules of equal length. They a re asked to denature the DNA molecules by heating. The DNA given to student A has the following composition of bases $(A:G:T:C::35:15:35:15)$ while that given to student $B$ is $(A:G:T:C::12:38:12:38)$. Which of the following statements is true?

• A. Both the DNA molecules would denature at the same rate
• B. The information given is insufficient to draw any conclusion
• C. DNA molecule given to student B would denature faster than that of student A
• D. DNA molecule given to student A would denature faster than that given to student B

Answer 1

Answer: (D)

In a DNA, adenine is paired with thymine with double bond and guanine is paired with cytosine with triple bond.
We know that double bonds are easier to break than triple bonds.
Student $A$ has more $A=T$ than $G=C$, while student $B$ has more $G=C$ than $A=T$.
Therefore, the $DNA$ molecule given to student $A$ would denature faster than that given to student $B$.