Biomolecules Question 52
52. Which is not consistent with double helical structure of DNA?
[1990]
(a) $A=T, C=G$
(b) Density of DNA decreases on heating
(c) $A+T / C+G$ is not constant
(d) Both A and B
Show Answer
Answer : c
Hints & Solutions
(c) The ratios for the $(A+G) /(T+C)$ are constant at approximately 1.0 for the different organisms. Each of these organisms contain a double stranded genome. The percentage of Guanine and Cytosine are almost equal to each other, similarly the percentages of Adenine and Thymine are almost equal to each other as well. In other words, the percentage of purines should be equal to the percentage of pyrimidines for double stranded DNA. This means that $(A+G)=(C+T)$ The $(A+T) /(C+G)$ ratios are not constant for all the species The relative numbers of $(A+T)$ base pairs and $(G+C)$ base pairs are unique to each organism and can vary between the different species.
