Question

If a strand of DNA has 45% A, what percent will be C?

Answer 1

55%

Step-by-step explanation:

Answer 2

`\boxed {\boxed {\sf C=5\%}}`

Step-by-step explanation:

There is a method to calculating base percentages known as Chargaff's Rule. It states:

`A+T+G+C=100\%`

We know the DNA has 45% Adenine or A.

Adenine always pairs equally with Thymine. In other words, the percentage of adenine equals the percentage of thymine (45% Thymine or T).

`45\%+45\%+C+G=100\%`

`90\%+C+G=100\%`

Subtract 90% from both sides.

`90\%-90\%+C+G=100\%-90\%`

`C+G=10\%`

Cytosine(C) and Guanine(G) pair equally and their percentages will be equal. We can divide 10% by 2.

`C+G=10\% /2`

`C/G=5\%`

The percentage of Cytosine or C is 5 percent.