This means that 18% of the bases in this DNA molecule are guanine. True False
The correct answer and explanation is:
Answer: True
Explanation:
In double-stranded DNA, the base pairing rules, known as Chargaff’s rules, state that:
- The amount of adenine (A) equals the amount of thymine (T).
- The amount of guanine (G) equals the amount of cytosine (C).
This is because A pairs specifically with T, and G pairs specifically with C through hydrogen bonds.
If the statement says 18% of the bases are guanine, then by Chargaff’s rules, 18% must also be cytosine. Together, guanine and cytosine make up:
- 18%+18%=36%18\% + 18\% = 36\% of the total bases.
Since all the bases must add up to 100%, the remaining bases are adenine and thymine, which together account for:
- 100%−36%=64%100\% – 36\% = 64\%.
Because A = T, adenine and thymine individually make up:
- 64%2=32%\frac{64\%}{2} = 32\% each.
So the base composition of the DNA would be approximately:
- Adenine (A): 32%
- Thymine (T): 32%
- Guanine (G): 18%
- Cytosine (C): 18%
This matches the fundamental pairing principle of DNA and validates that if 18% of the bases are guanine, the statement is true.
Additional context:
The complementary base pairing ensures DNA’s double helix structure is stable and allows accurate replication during cell division. This precise pairing means that knowing the percentage of one base automatically lets you know the percentage of its complementary base.
For example, if you know guanine is 18%, cytosine is also 18%. The rest of the bases are adenine and thymine in equal amounts. This is a fundamental concept used in molecular biology, genetics, and biochemistry to understand DNA composition and function.