Question

Imagine that you are studying a newly discovered bacterium from a hot spring in Yellowstone National

Park. When you examine the nucleotide composition of this organism, you find that 10% of the
nucleotides in its DNA are adenine. What is the percentage of guanine nucleotides in this segment?
A)80%.
B)10%.
C)90%.
D)40%.

Answer 1

For a bacterium with 10% adenine in its DNA, Chargaff's rules dictate that there will also be 10% thymine and the remaining 80% is split evenly between guanine and cytosine, resulting in 40% guanine.

Step-by-step explanation:

In this scenario, you are analyzing the DNA of a bacterium found in a hot spring. Based on the information given, 10% of the nucleotides are adenine (A). According to Chargaff's rules, the amount of adenine is always equal to the amount of thymine (T), and the amount of guanine (G) is always equal to the amount of cytosine (C). As DNA is a double helix, each strand will have complements of these bases, meaning if there is 10% adenine, there will also be 10% thymine on the opposite strand. Therefore, the remaining 80% of the nucleotides must be divided equally between guanine and cytosine, leading to 40% guanine and 40% cytosine.

The correct answer to what percentage of the nucleotides in this segment of the bacterium's DNA is guanine is 40%, which corresponds to option D.