Final answer:
The correct relationship between the percentages of bases in a double-stranded DNA molecule is represented by the complementary base pairings of adenine (A) with thymine (T) and guanine (G) with cytosine (C), leading to the relation A/G = T/C.
Step-by-step explanation:
When considering the percentages of bases in a double-stranded DNA molecule, it is important to remember that each base of adenine (A) pairs with a base of thymine (T), and each base of guanine (G) pairs with a base of cytosine (C). This is due to base-pairing rules, which result from the hydrogen bonding capacities of the nucleotide bases and the geometric restrictions of the DNA double helix structure. The correct relationships between the percentages of nucleotide bases in the double-stranded DNA molecule can be represented by the base pairings A=T and G=C due to the complementary base-pairing nature of DNA.
- A + T = G + C is not correct because it suggests that the combined percentage of A and T equals the combined percentage of G and C, which is not necessarily true due to variations in base composition between species.
- (A + T)/(C + G) =1.0 is also not correct because the ratio of A + T to C + G may vary between species.
- A/C = G/T is not correct because it implies a constant ratio between A and C and between G and T across different DNA molecules, which is not the case.
- A/G = T/C is the correct relation because it expresses the complementary base pairing, where for every adenine there is a thymine, and for every guanine, there is a cytosine, keeping the ratios equal.
Example:
If 30% of the bases within a DNA molecule are adenine (A), then the percentage of thymine (T) would also be 30%, reflecting the complementary nature of these bases.