Answer:
Sample A: Thymine= 20.7%
; Adenine= 20.7%; Guanine = 29.3%
; Cytosine= 29.3%
Sample B: Thymine= 30.9%
; Adenine= 30.9% ; Guanine= 19.1%
; Cytosine base= 19.1%
Explanation:
In a double-stranded DNA molecule, the percentage of adenine base is equal to that of the thymine base while the percentage of guanine base is equal to that of the cytosine base. It is called Chargaff's rule and is based on the complementary base pairing of purine and pyrimidine bases.
Sample A: Percentage of thymine= 20.7%
This means that the sample has= 20.7% adenine base
Total thymine and adenine bases in sample A= 20.7 + 20.7 = 41.4%
Therefore, proportion of guanine + cytosine bases in the sample= 100-41.4= 58.6%
Percentage of guanine base= 58.6/2 = 29.3%
Percentage of cytosine base= 29.3%
Sample B: Percentage of thymine= 30.9%
This means that the sample has= 30.9% adenine base
Total thymine and adenine bases in sample A= 30.9 + 30.9 = 61.8%
Therefore, proportion of guanine + cytosine bases in the sample= 100-61.8= 38.2%
Percentage of guanine base= 38.2/2 = 19.1%
Percentage of cytosine base= 19.1%
