Question

A sample of cow dna is taken. this sample contains 20% adenine and 30% cytosine what are the percentages of thymine and guanine?

a. thymine: 20% guanine: 20%
b. thymine: 20% guanine: 30%
c. thymine: 30% guanine: 20%
d. thymine: 25% guanine: 25%

Answer 1

Based on Chargaff's rules, the DNA sample from a cow with 20% adenine must have 20% thymine, and with 30% cytosine, it must have 30% guanine, corresponding to option B.

Step-by-step explanation:

The question asked concerns the percentage of different nucleotide bases in a cow DNA sample, based on Chargaff's rules. According to these rules, the amount of adenine (A) is always equal to thymine (T), and the amount of guanine (G) is equal to cytosine (C). If the DNA sample contains 20% adenine, then it must also contain 20% thymine. Given that the sample has 30% cytosine, it must similarly have 30% guanine. Consequently, the correct percentages of thymine and guanine in the cow DNA sample are:

• Thymine: 20%
• Guanine: 30%

This answer corresponds to option B. thymine: 20%, guanine: 30% from the provided choices.