Molecular Basis Of Inheritance Ques 159
159. 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 :
(a) G $17 \%, A 16.5 \%$, T $32.5 \%$
(b) G $17 \%, A 33 \%$, T $33 \%$
(c) G $8.5 \%$, A $50 \%$, T $24.5 \%$
(d) G $34 \%$, A $24.5 \%$, T $24.5 \%$
Show Answer
Answer : b
Hints & Solution
(b) Chargaff’s rule states that $A=T$ and $G$ $\equiv C$. The molar amount of adenine $=$ molar amount of thymine. The molar amount of guanine $=$ molar amount of cytosine. Hence, $G$ is $17 \%, \quad$ so, $C=17 \%$ $ A=33 \%, \quad \text{ so, } T=33 \% $
BETA
