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 28.7 % thymine. Assume the organisms contain normal double‑stranded DNA and predict the composition of the other bases.sample A contains 21.1% Thymine - %A
sample B contains 27.1% Thymine - %A
number - %G
number - %G
number - %C
number - %C
Both samples are then denatured to remove the secondary structure.which will have the higher temperature to denature A or B ?

Answer 1

Answer:

Sample A

T= 21.3% and A= 21.3%

G=28.7% and C= 28.7%

SAMPLE B

T=28.7% and  A= 28.7%

G= 21.3% and C= 21.3%

Sample A would have higher melting temperature

Explanation:

According to given information, sample A contains 21.3% thymine.

Percentage of adenine in sample A= 21.3% (Since adenine base pairs with thymine, so, adenine and thymine are present in equal amount in a double stranded DNA)

Total of A+T in sample A= 21.3 + 21.3 = 42.6%

G+ C content of sample A= 100-42.6= 57.4%

Percent G content of sample A = 57.4/2 = 28.7%

Percent C content of sample A = 28.7%

SAMPLE B:

According to the given information, sample B contains 28.7% thymine.

Therefore, percent of Adenine base in sample B= 28.7%

Total of A+T content in sample B= 28.7 + 28.7 = 57.4%

G + C content of the sample B = 100-57.4= 42.6%

Percent G content of the sample B= 42.6/2= 21.3%

Percent C content of sample B = 21.3%

There are three hydrogen bonds between a GC pair while there are only two hydrogen bonds between AT pair. The DNA content with higher GC content has higher melting temperature. Therefore, sample A would have higher melting temperature.