Question

complementary base pairing. but, since rna does not contain thymine, uracil pairs with adenine. this model shows how rna nucleotides pair with dna nucleotides. complete the paragraph to summarize how an rna molecule is created. first, a section of the dna molecule is unzipped. then, rna nucleotides are brought in to pair with the dna nucleotides. according to the rules of complementary base pairing, __ pairs with thymine, and guanine pairs with . but rna contains the base uracil instead of . uracil pairs with __. (options: adenine, thymine, cytosine, guanine)

Explanation:

1. For the first blank (pairs with thymine): In DNA - RNA base pairing, adenine (A) pairs with thymine (T) (in DNA, and in RNA synthesis, RNA's adenine pairs with DNA's thymine). So the first blank is adenine.
2. For the second blank (guanine pairs with): Guanine (G) pairs with cytosine (C) in both DNA - DNA and DNA - RNA base pairing. So the second blank is cytosine.
3. For the third blank (RNA has uracil instead of): RNA has uracil (U) instead of thymine (T) (since DNA has thymine and RNA has uracil as the equivalent pyrimidine). So the third blank is thymine.
4. For the fourth blank (uracil pairs with): Uracil (U) pairs with adenine (A) (since in RNA - DNA pairing, U takes the place of T, and T pairs with A, so U pairs with A). So the fourth blank is adenine.

Answer:

1. adenine
2. cytosine
3. thymine
4. adenine