In one DNA molecule, the proportion of thymine nucleotides is 18% of the total number of nucleotides.
In one DNA molecule, the proportion of thymine nucleotides is 18% of the total number of nucleotides. Determine the amount (in%) of each of the other types of nucleotides.
To solve the problem, one should recall the principle of complementarity of nitrogenous bases. In the deoxyribonucleic acid molecule, thymine forms bonds with adenine, and guanine with cytosine. According to the condition of the problem, thymine in this DNA molecule contains 18%. Accordingly, adenine is 18%. The total content of guanine and cytosine will be:
C + G = 100% – (18% + 18%) = 64%.
Since hyuanine and cytosine form complementary pairs, the cytosine content is equal to the guanine content and is:
G = C = 64% / 2 = 32%.
Answer: this DNA molecule contains: adenine – 18%, guanine – 32%, cytosine – 32%.