Question

A certain DNA sample is found to have a makeup consisting of 22% thymine. Use Chargaff’s rules to fill in the percentages for the other three nitrogenous bases.

Answer 1

If a DNA sample consists of 22% thymine, then according to Chargaff's rules it will also contain 22% adenine and 28% each of guanine and cytosine.

Step-by-step explanation:

Based on Chargaff's rules, if a DNA sample has 22% thymine, the amount of adenine would also be 22% because adenine (A) pairs with thymine (T) in the DNA structure. Since the percentages of guanine (G) and cytosine (C) must be equal (G=C), and the total of all four bases must add up to 100%, the remaining percentage is divided between guanine and cytosine.

This means that each should be 28%, calculated as 100% - 22% (adenine) - 22% (thymine) = 56%, and 56% / 2 = 28% for both guanine and cytosine.

Answer 2

Adenine= 22%

Guanine= 28%

Cytosine = 28%

Step-by-step explanation:

According to Chargaff rule, the amount of adenine in a double-stranded DNA is equal to the amount of thymine. This is due to the fact that adenine and thymine bases are complementary and form base pairs.

Likewise, the amount of guanine in a double-stranded DNA is equal to the amount of cytosine since guanine pairs with cytosine.

Given that percentage of thymine in a DNA sample = 22%

Percentage of adenine = 22%

Total percentage of adenine and thymine = 22+ 22 = 44%

Percentage total of guanine and cytosine bases = 100-44 = 56%

Percentage of guanine base in the DNA = 56 /2 = 28%

Percentage of cytosine base in the DNA = 28%