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 21.3 % thymine and sample B contains 27.7 % thymine.Assume the organisms contain normal doubleâstranded DNA and predict the composition of the other bases..Percent adenine in sample A:

Answer 1

Sample A: 21.3%A, 28.7% G and 28.7% C

Sample B: 27.7% A, 22.3% G and 22.3% C

Step-by-step explanation:

According to Chargaff's rules of base pairing, the amount of adenine in a DNA molecule equals the amount of thymine, and the amount of G=C.

Sample A

Contains 21.3% T, so it also contains 21.3% A. Therefore A+T= 42.6%

100% - (A+T) = (G+C)

100% - 42.6% = 57.4%

G+C add up to 57.4% of the DNA in sample A. And because G=C, there's 28.7% G and 28.7% C.

Sample B

Contains 27.7% T, so it also contains 27.7% A. Therefore A+T= 55.4%

100% - 55.4% = 44.6%

G+C add up to 44.6% of the DNA in sample B.

And G=C, so there's 22.3% G and 22.3% C.