Genetics Chapter 17 Notes: Translation & Protein Synthesis

Lecture 17
Translation &
Protein Synthesis




BI333: General Genetics
Dr. Matt Arterburn
Department of Biology

,FEATURES OF THE GENETIC CODE
• The genetic code is based on linear nucleotide sequence and has the
following features:
TRIPLETS
Composed of codons (nucleotide triplets),
complementary to anticodons of tRNAs

NONOVERLAPPING
Each nucleotide belongs to 1 codon

DEGENERATE
All but two amino acids are specified by
multiple codons

ORDERED
Multiple codons for the same amino acid are
similar (differ by a single nucleotide)

UNIVERSAL
There are some exceptions, but codons
have the same meanings in all organisms

,
, DISCOVERY OF THE GENETIC CODE
• Research from 1954 (discovery of DNA) into the 1960’s was focused on
deciphering the genetic code (how DNA translated into proteins)

• 3-nt per codon made sense, because 42 = 16 and 43 = 64, so a 3-nt codon is
the simplest combination that codes for all 20 amino acids

• Crick et al (1961) provided WILD-TYPE
evidence that codons Glu-Glu-Glu-Glu
consisted of 3 nt
MUTANT
• Inserted one or two
nucleotides into a gene and Glu-Asp-Gly-Gly
caused a frameshift
mutation
WILD-TYPE
• Insertion of three Glu-Glu-Glu-Glu
nucleotides created an
extra amino acid, but the MUTANT
frame was corrected (wild-
Glu-Asp-Gln-Glu-Glu
type phenotype restored)