Chapter 12, Problem 26A

Summary Introduction

Introduction:

The central dogma of biology is that the DNA codes for RNA which guides the synthesis of proteins. RNA is nucleic acid similar to DNA but in RNA the base uracil replaces thymine, and it is single stranded. Three major types of RNA re found in living cells; messenger RNA (mRNA), ribosomal RNA (rRNA) and transfer RNA (tRNA).

Answer to Problem 26A

Correct answer :

The correct answer is option B. 5’ AUGUUUGAUCUU3’.

Explanation of Solution

Explanation/justification for the correct answer:

Option B. 5’AUGUUUGAUCUU3’- Through transcription, the DNA code is transferred to mRNA. The mRNA transcript is manufactured in a 5’ to 3’ direction adding each new nucleotide to the 3’ end. Free RNA nucleotides base pairs with their complementary nucleotides on the DNA strand. Uracil is incorporated instead of thymine as the mRNA molecule is made.

Hence, this is the correct option.

Explanation for incorrect answer:

Option A. 5’ATGTTTGATCTT3’- Uracil is incorporated instead of thymine as the mRNA molecule is made. In this option there is thymine and no uracil. Hence, this is not the correct option.

Option C. 5’TACAAACTAGAA3’- Through transcription the DNA code is transferred to mRNA. The mRNA transcript is manufactured in a 5’ to 3’ direction adding each new nucleotide to the 3’ end. This is the same sequence of nucleotides as the template strand of DNA. There is no base pairing done in the mRNA. Hence, this is not the correct option.

Option D. 5’UACAAACUAGAA3’- Uracil is incorporated instead of thymine as the mRNA molecule is made. In this option only thymine is replaced by uracil but no complementary base pairing is done in mRNA. Hence, this is not the correct option.