Question

In samples of DNA isolated from two unidentified species in bacteria, X and Y adenine makes up 32% and 17%, respectively, of the total bases. What relative proportions of adenine, guanine, thymine, and cytosine would you expect to find in the two DNA samples? What assumptions have you made? One o the species was isolated from a hot spring (64°C). Suggest which species is the thermophilic bacterium and explain your choice in DETAIL.

Answer 1

Answer:

On the basis of Chargaff's rule, in a double-helical DNA, A = T and G = C (Here A means adenine, T means thymine, G means guanine, and C means cytosine. For X, A is given 32%, therefore, T must be 32%, and the leftover 36% is to be distributed equally between G and C. Thus, G = C = 18% each.  

The assumption formed is that the DNA is a double-stranded structure. The species that exhibits higher G + C content in the molecule of a DNA is steadier at higher temperatures as it melts at high temperature. The species Y, which exhibits G + C in total as 66% is the thermophilic bacterium between the two.