Question

A strand of dna contains 10% adenine. what percentage of cytosine must be present in this strand of dna then?

a) 80%
b) 40%
c) 10%
d) 20%

Answer 1

`\boxed {\boxed {\sf B. \ 40 \% \ cytosine}}`

Step-by-step explanation:

First, recall the base pairs in DNA:

• Adenine and Thymine
• Cytosine and Guanine

We know this strand of DNA has 10% adenine. Since A and T pair, there must also be 10% guanine.

So, A and T make up 20% of the DNA strand.

That leaves 80% for cytosine and guanine. They are pairs, so they share this percentage equally.

• 80/2 =40

There must be 40% cytosine and 40% guanine.

The strand of DNA has 40% cytosine