Chapter 13, Problem 26ESP

(a)

Summary Introduction

To determine: The evidence that supports the doublet code notion.

Introduction: The mRNA consists of many bases. A collection of three bases that has the capability to code for a particular amino acid is called codon. Codons are present in the mRNA. These codons attach with the anticodon part of tRNA to synthesize amino acid. The anticodon part of tRNA is complementary to the codon part of mRNA.

(b)

Summary Introduction

To determine: The ways by which “early” amino acids are important in terms of the evolution of genetic code.

Introduction: Transcription is the process by which DNA converts into pre-mRNA. The pre-mRNA undergoes post-transcriptional changes and converts into a mature mRNA. The next step after post-transcriptional changes is translation. It is the process by which the mRNA converts into amino acids. The collection of three bases present on the mRNA that codes for a specific protein is called codon. The amino acids join together by polypeptide bond to form protein molecules.

(c)

Summary Introduction

To determine: Whether the fact that “cysteine, tyrosine, and phenylalanine have only two codons” is a coincidence.

Introduction: A codon can code only for a single amino acid, but an amino acid can be coded by more than one codon. For example, GCU codes for alanine only, but alanine can be coded by GCU, GCC, GCA, and GCG codons.