Question

Bacteria and other microbes can be used to "clean up" an oil spill by breaking down oil into carbon dioxide and water. Two samples isolated from the Deepwater Horizon leak in the Gulf of Mexico were labeled A and B. The DNA of each was isolated and the percent thymine measured in each sample. Sample A contains % thymine and sample B contains % thymine. Assume the organisms contain normal double‑stranded DNA and predict the composition of the other bases.

Answer 1

According to the Chargaff rule, A pairs with T and G pairs with C. So, the purine to pyrimidine ratio is 1:1. For example, in sample of A: As A contain 21.1% adenine, so since A = T = 21.1% and A+T = 42.2 %. Thus, G+C = 57.8 % So, G = 57.8/2 = 28.9 % Also, G = C = 28.9 % In sample of B, As A contain 27.1% adenine, so since A = T= 27.1% Also, A+T = 54.2 % Thus, G+C = 45.8 % So, G = 57.8/2 = 22.9 % Also, G = C = 22.9 % %3D Since, the GC content is more in the sample A i.e. 57.8%. Therefore, the sample A have the higher temperature to denature than B (45.8%). [Note: if your problem has different % then please follow this process to calculate the answer]