Question

question 53
1.5 pts
which of the following statements correctly describes one of chargaffs rules regarding dna?
the percentages of adenine and cytosine are roughly equal, as are the percentages of guanine and thymine in the dna of a given species.
dna has a double helical structure.
dna base composition does not vary between species.
the percentages of adenine and thymine are roughly equal, as are the percentages of guanine and cytosine in the dna of a given species.

Explanation:

1. Recall Chargaff's rules: In DNA, the amount of adenine (A) equals thymine (T), and guanine (G) equals cytosine (C) in a given species.
2. Analyze each option:

• First option: A should equal T, G equal C, not A - C and G - T. Incorrect.
• Second option: Double - helix structure is from Watson - Crick model, not Chargaff's rule. Incorrect.
• Third option: DNA base composition varies between species (another part of Chargaff's findings), so this is wrong.
• Fourth option: Matches Chargaff's rule (A=T, G=C in a species). Correct.

Answer:

The percentages of adenine and thymine are roughly equal, as are the percentages of guanine and cytosine in the DNA of a given species.