Question

in your own words
during transcription, in dna, the thymine base (t) is replaced by another base. what is it?
uracil (u) is similar to thymine but lacks a methyl group. in rna, uracil pairs with adenine using two hydrogen bonds. in dna, thymine pairs with adenine using two hydrogen bonds.
in the image below, thymine (t) in dna is replaced by uracil (u) in rna.
(dna sequence and rna sequence image)
what replaces thymine (t) in rna?

• adenine (a)
• uracil (u)
• guanine (g)

Explanation:

The problem is about the nucleotide that replaces thymine (T) in RNA. From the provided text and image (showing transcription where DNA's T is replaced by RNA's U), and knowledge of nucleic acid structure: in RNA, uracil (U) takes the place of thymine (T) that is present in DNA. Adenine (A) pairs with thymine/uracil, and guanine (G) pairs with cytosine (C), so they don't replace T.

Answer:

B. uracil (U)