Neet Solved Paper 2015 Question 79
Question: In sea urchin DNA, which is double stranded 17% of the bases were shown to be cytosine. The percentages of the other three bases expected to be present in this DNA are
Options:
A) G/34%, A/24.5%, T/24.5%
B) G/17%, A/16.5%, T/32.5%
C) G/17%, A/33%, T/33%
D) G/8.5%, A/50%, T/24.5%
Show Answer
Answer:
Correct Answer: C
Solution:
In double-stranded DNA, the amount of cytosine (C) is equal to the amount of guanine (G), and the amount of adenine (A) is equal to the amount of thymine (T). This is due to the base-pairing rules where C pairs with G and A pairs with T.
Given that 17% of the bases are cytosine (C), it follows that 17% of the bases are also guanine (G).
Since C and G together make up 34% of the bases (17% + 17%), the remaining 66% of the bases must be adenine (A) and thymine (T) in equal amounts. Therefore, adenine (A) will be 33% and thymine (T) will be 33%.
So, the percentages of the other three bases expected to be present in this DNA are:
- Guanine (G): 17%
- Adenine (A): 33%
- Thymine (T): 33%
BETA
