Question

deciphering dna
rat\t28.6%\t21.5%\t21.4%\t28.4%
wheat\t27.3%\t22.8%\t22.7%\t27.1%
grasshopper\t29.3%\t20.7%\t20.5%\t29.3%
at the time, chargaff did not know why the amounts of these pairs of nucleotides were similar. however, his work inspired other scientists to explore dnas structure more fully.
question 4 dok 2 aligned standards 5 points
what evidence best supports that specific nucleotides have a 1:1 ratio?
select an answer
the percentage of adenine and cytosine is about the same in an organism.
the percentage of adenine and thymine is about the same in an organism.
rats have more thymine than other organisms.
humans have more guanine than other organisms.

Explanation:

To determine which evidence supports specific nucleotides having a 1:1 ratio, we use Chargaff's rules. Chargaff's rules state that in DNA, the amount of adenine (A) is equal to thymine (T), and guanine (G) is equal to cytosine (C) (A=T, G=C).

• Option 1: Adenine and cytosine do not follow a 1:1 ratio (A≠C), so this is incorrect.
• Option 2: Adenine and thymine (A and T) have a 1:1 ratio (A=T) according to Chargaff's rules, so this is correct.
• Option 3: The table shows rats' nucleotide percentages, but there's no indication rats have more thymine than others, and this doesn't relate to a 1:1 ratio of specific nucleotides.
• Option 4: There's no data or rule supporting humans having more guanine than others, and this doesn't relate to a 1:1 ratio.

Answer:

B. The percentage of adenine and thymine is about the same in an organism.