Chapter 26, Problem 26.73CP

Interpretation Introduction

Interpretation:

The case of a protein that does not include methionine as its first amino acid has to be accounted.

Concept Introduction:

RNA synthesis: The process of RNA synthesis is Transcription. A small section of DNA unwinds, only one of the two strands act as template and the other strand as informational strand. The complementary bases are attached one by one by the action of RNA polymerase at template strand on moving down. The newly generated RNA is the exact copy of the informational strand, with the exception that a U replaces each T in the template DNA. The RNA synthesised carries genetic information and directs protein synthesis.

Codon: A sequence of three ribonucleotides in the mRNA chain that codes for a specific amino acid; also a three-nucleotide sequence that is a stop codon and stops translation.

Genetic code: The sequence of nucleotides, coded in triplets (codons) in mRNA that determines the sequence of amino acids in protein synthesis.

Illustrated relationships are:

DNA informational strand: 5’ ATG  CCA   GTA  GGC  CAC   TTG   TCA  3’

DNA Template strand:         3’ TAC  GGT   CAT  CCG  GTG   AAC   AGT  5’

mRNA:                                  5’ AUG  CCA  GUA  GGC  CAC  UUG   UCA  3’

protein:                                       Met    Pro     Val    Gly     His    Leu      Ser

Notice: 5’ end of the mRNA strand codes for the N-terminal amino acid, whereas the 3’ end of the mRNA strand codes for the C-terminal amino acid. Proteins are always written N-terminal to C-terminal, reading left to right.