In the mRNA sequence provided, what is the DNA sequence complementary to the first four bases in this section?

In the mRNA sequence provided, what is the DNA sequence complementary to the first four bases in this section?

• A. GGAC
• B. CCAG
• C. CAGG
• D. CTGA

Answer: (B)

Understanding how mRNA bases pair with DNA bases to form a complementary sequence. Each RNA base finds its DNA partner: G pairs with C, U pairs with A, and C pairs with G. To get the DNA sequence complementary to the first four bases of the mRNA, substitute each base with its DNA partner: G becomes C, the second G becomes C, U becomes A, and C becomes G. Put together, that gives CCAG. This is why CCAG fits—the four mRNA bases GGUC pair with CCAG on the DNA template. The other sequences would arise from different RNA bases in those positions, so they wouldn’t match the given mRNA segment.

Understanding how mRNA bases pair with DNA bases to form a complementary sequence. Each RNA base finds its DNA partner: G pairs with C, U pairs with A, and C pairs with G. To get the DNA sequence complementary to the first four bases of the mRNA, substitute each base with its DNA partner: G becomes C, the second G becomes C, U becomes A, and C becomes G. Put together, that gives CCAG. This is why CCAG fits—the four mRNA bases GGUC pair with CCAG on the DNA template. The other sequences would arise from different RNA bases in those positions, so they wouldn’t match the given mRNA segment.