A species has 29% of its DNA composed of the nucleotide containing guanine (G). What percent does the nitrogen base thymine (T) equal?

T = 21%

Explanation:

In DNA base pairing; Adenine will always pair with Thymine & Guanine will always pair with cytosine. Now, Given that a species has 29% of its DNA composed of the nucleotide containing guanine (G), we can therefore say that 29% of the bases are also cytosine. Hence, there will exist many guanine bases as cytosine bases.

G = 29%, C = 29%, A=?, T=?

G + C + A + T = 100%

29 + 29 + A + T = 100%

58 + A + T = 100%

A + T = 100% - 58%

A + T = 42%

In respect to cytosine and guanine, adenine and thymine must also be present in equal proportions in order to form proper base pairs.

We can therefore reasonably assume that half of the remaining DNA will consist of each residue.

As such, A = 21%, T = 21%