BIO1022 Lecture Notes - Lecture 2: Tata Box, Chromatin, Cyclic Adenosine Monophosphate
30 May 2018
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BIO1022 Lecture 2 – Regulation of Gene Expression
- mutations
• differs from highly common wt
• nucleotide pair substitution - change of a nucleotide pair
•
o silent - no effect on the amino acid sequence - redundancy in the
code - all code for same protein - same position
o missense - range of effects depending on the location within the
protein and the identity of the new amino acid
o nonsense - effect depends on how close the mutation is to the wild-
type stop codon - where the translation stops - effect on function
• nucleotide-pair insertion or deletion
•
o 1 nucleotide pair insertion - immediate nonsense
o 1 nucleotide pair deletion - extensive missense - effect amino acids
down the line
o 3 nucleotide pair deletion - no frameshift - one amino acid is
missing
• effects
•
o truncation - stop codon - proteins missing - mild to moderate effect
o metal co-factor - unable to bind
o ligands - another protein - lipid - hormone - unable to bind -
receptor protein affected - loss of function
o transcription factor - proteins that bind to DNA - on-off
• causes
•
o oxidative damage from normal cellular metabolism
o errors in the process of DNA replication or DNA recombination
o chemicals - chemical mutagens, chemicals in tobacco
o radiation - UV, X-ray, Gamma
- polymorphisms - variations
- regulation of gene expression
• alternative splicing
• prokaryotes
•
o operon - consists of multiple genes
o operator and
o promotor - RNA polymerase binds and initiates transcription
o tryptophan - trp operon
o
▪ when protein present - protein acts a co-repressor - binds
to inactive repressor protein - binds to the operator - RNA
polymerase cant proceed to transcribe the operon
▪ repressible system - repression of the operon
▪ negative regulation
o lac operon of E.coli
o
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