Control of Gene Expression Flashcards
What are three types of gene regulation?
Pre-transcription control, post-transcription control and translational control
What is a transcription factor?
Protein produced by regulatory genes that controls gene expression
What functions can transcription factors do?
Block attachment of RNA polymerase (blocking expression of gene)
Alter (increase/decrease) rate of gene expression
What occurs during post-transcription control?
Depends on non-coding DNA - controls rate or blocks trimming, capping and tailing of mRNA. If non-coding introns are not removed correctly, mRNA will be broken down.
Non-coding RNAs can form double helix -> can’t be read
Receptors on pores can block passage to cytoplasm (no access to ribosomes)
miRNA (micro RNA) - binds to 3’ untranslated site -> silences gene (reduces expression)
What occurs during translational control?
Increase/decrease rate via controlling the amounts of molecules (amino acids and proteins)
Amount of time RNA survives before degradation
What are constitutive genes?
Always switched on
What are structural genes?
Code for proteins and RNAs not involved in gene regulation (e.g. can code for enzymes, protein channels etc.) -> performs a structural role in a cell (e.g. digestion)
What are regulatory genes?
Code for transcription factors and controls expression of genes
Give examples of regulatory genes?
HOX genes, sex determining region Y (SRY), Tumor suppressor genes, alternate splicing, LacL (repressor for lac operon)
What are HOX genes?
Known as master regulatory gene
Control formation of segmentation of embryonic body plan
HOX proteins (products of HOX genes) determine type of tissue/appendage that will form on a segment -> but do not form actual segments themselves
What are SRY genes?
Produces transcription factor that binds to specific regions of DNA and is responsible for production of male gonads in foetus
Production male sex hormones (testosterone)
Inhibits production of female sex hormones (estrogen) and overrides production of female reproductive organs
What is Lac operon?
Found in E.coli and other bacteria
Inducible operon switches on when lactose present
Operon expresses structural genes for 3 enzymes
enzymes then help break down lactose
Lac repressor prevents RNA polymerase binding to operator - switched off
What are tumor-suppressor genes?
Proteins they encode can prevent uncontrolled cell growth
Produced in response to exposure to radiation and chemicals that cause damage to structure of DNA
Will bind to DNA to repress genes that play role in continuation of cell cycle -> inhibits cell division -> prevents DNA replicating
If damage cannot be repaired -> initiates cell death (apoptosis)
What does epigenome refer to?
“Above genome”
Factors affect part of the DNA activated -> these factors may occur from extra or intracellular stimuli (neighbouring cells, physiology, environment)
What results from epigenetic modifications?
Add methyl/acetyl groups to DNA (DNA tags) or histones in chromatin (histone modification)
Chemical changes affect how DNA coiled and results in changes in gene expression/variations in phenotype as transcription/translation processes altered. These changes are results of environmental conditions
