Question

33. A certain DNA molecule is determined to have a guanine content of 40 percent. If a RNA molecule is synthesized from this particular DNA, what percentage of uracil will be in the RNA?

A. 40%
B. 60%
C. 20%
D.10%

Answer 1

The RNA molecule synthesized from a DNA molecule with 40 percent guanine content will have 20 percent uracil because adenine, which pairs with uracil in RNA, will occupy the remaining 20 percent of the bases.

Step-by-step explanation:

If a DNA molecule has a guanine (G) content of 40 percent, because of complementary base pairing, we know that cytosine (C) also makes up 40 percent of the DNA, since guanine and cytosine pair together in DNA. As DNA and RNA share the pairing of guanine with cytosine, the RNA synthesized from this DNA will also have 40 percent cytosine. Since adenine pairs with thymine in DNA and with uracil in RNA, the remaining 20 percent of DNA that is adenine will pair with 20 percent uracil in the transcribed RNA. Therefore, the RNA molecule synthesized from this DNA will have 20 percent uracil.