gene regulation and developmental genetics in eukaryotes Flashcards
1
Q
transcriptional regulation of gene expression in eukaryotes
A
- similar to prokaryotes, the ability of RNA polymerase to transcribe it
- often complex combinations of transcription factors to regulate single genes, as they have far more genes and more complex patterns of gene expression than prokaryotes
- DNA has to be unwound from histones before transcription, giving another layer of regulation
2
Q
general transcription factors
A
- RNA polymerase and other associated proteins
- bind to promoter-proximal elements
- affects expression of many genes downstream
3
Q
specific transcription factors
A
- bind to enhancers often a long way from promoters
- regulate small subsets of genes
- often only active in certain cell types
- e.g. GAL system in yeast
4
Q
transcriptional regulation using specific transcription factors, GAL system in yeast
A
- relatively simple as yeast is unicellular
- structural genes GAL1,2,7,10 encode enzymes for galactose metabolism (galactose into glucose)
- regulatory gene GAL4 produces sequence-specific DNA binding protein Gal4 that binds to enhancer (Upstream Activating Sequence), allowing structural genes to be transcribed
- regulatory gene GAL80 produces regulatory protein Gal80 which binds to Gal4, preventing it from activating transcription
- galactose binds to allosteric site of Gal3 protein, which binds to Gal80 causing it to release Gal4, allowing the transcription of structural genes
5
Q
post-transcriptional regulation of gene expression
A
- manipulation of mRNA including splicing
- post-translational modification
- introns and exons
6
Q
reporter gene
A
- useful gene that produces protein where the level of expression is easily measured
- e.g. green fluorescent protein (GFP) from jellyfish (concentration is proportionate to amount of light emitted)
- inserted downstream of regulatory protein binding site, so expressed at the same time as target gene (expression being measured)
7
Q
properties of model organisms for the study of developmental genetics
A
- short life cycle
- short generation times
- easy to rear in lab
8
Q
homeotic mutants
A
- mutation of single key gene determining body plan
- has a dramatic effect on development
- useful for identifying key genes for determining body plans
9
Q
homeotic mutants in Drosophilia
A
- Bithorax mutation = 2 pairs of wings, halteres resemble hind wings
- Antennapedia mutation = antennae resemble legs
10
Q
homeotic mutants in mice
A
- Hoxa11 and Hoxd11 mutation
= sacral (hip) vertebrae transformed into lumbar (lower back) vertebrae, no back legs
11
Q
homeobox
A
- 180 nucleotide sequence of homeotic genes that is shared by all animals
- contains hox genes that code for hox proteins
- hox proteins are sequence-specific DNA binding proteins that act as transcription factors, controlling gene expression within the development of body plans
12
Q
hox genes in drosophilia
A
- form 2 gene complexes on 3rd chromosome
- bithorax = 3 hox genes
- antennapedia = 5 hox genes
13
Q
hox genes in mice
A
- 4 gene clusters all on different chromosomes
- 9-11 hox genes
- 2 duplications of ancestral cluster
14
Q
maternal effect genes
A
- expressed in mother and provided to egg
e.g. Bicoid in drosophilia - early embryo is syncytium, the membranes are incomplete so nuclei are contained in continuous cytoplasm
- Bicoid protein translated from maternal mRNA in egg when it is fertilised
- protein highly concentrated at anterior end
- diffuses to posterior, creating concentration gradient
- binds top promoters of other development genes, only activates transcription of gap genes at anterior of embryo
- mutants may lack anterior structures
15
Q
gap genes (drosophilia)
A
- affects formation of continuous blocks of segments to create a rudimentary body plan
- mutants lack segment blocks
