Chapter 26, Problem 23P

Interpretation Introduction

Interpretation:

The base sequence of the segment of DNA which is responsible for the biosynthesis of the given hexapeptide should be determined.

Concept introduction:

RNA is the abbreviation term of “Ribonucleic Acid”.  It is a complex molecule found in all living things.

RNA helps to make proteins.

Important RNAs such as messenger RNA (mRNA), rRNA (ribosomal RNA) and tRNA (transfer RNA) and their functions are mentioned below,

$\begin{array}{cc}\text{RNA}& \text{Function}\\ \text{mRNA}& \text{instructions}\text{to}\text{protein}\\ \text{rRNA}& \text{part}\text{of}\text{the}\text{ribosomes}\\ \text{tRNA}& \begin{array}{l}\text{carriers}\text{that}\text{match}\text{amino}\text{acids}\\ \text{to}\text{codons}\text{during}\text{translation}\end{array}\end{array}$

Codons are the sequence of three bases in mRNA that specifies the amino acid to be incorporated into a protein.

Some amino acids and their corresponding mRNA codons are listed below,

$\begin{array}{l}\begin{array}{cc}\text{Amino}{\text{acid}}^{\text{*}}& \text{mRNA}\text{codons}\\ \underset{\_}{\text{Ala}}\text{nine}& \text{GCU,GCC,GCA,GCG}\\ \underset{\_}{\text{Asp}}\text{aragine}& \text{GAU,GAC}\\ \underset{\_}{\text{Val}}\text{ine}& \text{GUU,GUC,GUA,GUG}\\ \underset{\_}{\text{His}}\text{tidine}& \text{CAU,CAC}\\ \underset{\_}{\text{Ser}}\text{ine}& \text{UCU,UCC,UCA,UCG}\\ \underset{\_}{\text{Arg}}\text{inine}& \text{CGU,CGC,CGA,CGG,AGA,AGG}\\ \underset{\_}{\text{Glu}}\text{tamic}\text{acid}& \text{GAA,GAG}\\ \underset{\_}{\text{Lys}}\text{ine}& \text{AAA,AAG}\\ \underset{\_}{\text{Gly}}\text{cine}& \text{GGU,GGC,GGA,GGG}\\ \underset{\_}{\text{Tyr}}\text{osine}& \text{UAU,UAC}\end{array}\\ \text{*}\text{The}\text{three}\text{letter}\text{code}\text{for}\text{each}\text{aminoacid}\text{is}\text{underlined}\text{.}\end{array}$

Anticodons are the matching sequence on the tRNA to the codon on the mRNA.  A base is nitrogen containing heterocyclic compound which is found in DNA and RNA.

There are mainly four nitrogen bases in RNA.

1. (1) Adenine
2. (2) Guanine
3. (3) Cytosine
4. (4) Uracil

In RNA, Adenine always makes a double bond with uracil ($A=U$) and cytosine always makes triple bond with guanine $\left(G\equiv C\right)$