Exam 2: Gene Regulation in Eukaryotes Flashcards
prokaryote genes vs. # eukaryote genes
prokaryotes have ~500-5000 genes
eukaryotes have ~6000-30,000 genes
how does genetic control begin?
with a promotor (both prokaryotes and eukaryotes)
promotor longer in eukaryotes
how is promotor strength determined?
binding affinity of the promotor
transcription factor
any protein that affects transcription (regulates gene expression)
how do transcription factors work?
bind a target site in DNA or bind another TF or both
what are TF DNA-binding sites called?
enhancers
can the same protein act as an activator or repressor in different circumstances?
yes
TFs can also act simultaneously in two places side by side on DNA
TF binding sites can be…
near promotors they regular
far away from promotors they regulate
upstream or downstream of transcription unit they control
can TF binding sites be in introns?
yes
two ways TF regulate genes
direct effects on the transcription complex
spreading effects on chromatin geometry
cis regulation sites
sites in DNA close to a gene, which code for TF binding sites
trans regulation sites
site in DNA far away from a gene, which code for TF proteins
what does trans mean
gene that codes for it is found somewhere else
it could be anywhere in the genome
what kind of effects do changes in the cis/trans part of the regulatory system have?
phenotypic effects
CRM
cis regulatory module/enhancer
cluster of TF binding sites
effects of CRM
converge on the promotor
what is a CRM
small region of DNA (500bp) with 5-15 binding sites for TFs
how long are the individual TF binding sites in a CRM
6-10 bases long
are CRMs on the same DNA as the gene they regulate?
yes, but they can be distant from the gene if they’re on the same dsDNA strand
are genes controlled by a single CRM or multiple CRMs?
either
why is on-off control of the same gene from different CRMs needed?
b/c many genes get used in more than one place
interactions between TFs that control genes by CRM
combinatorial control
cumulative effects
competitive binding
how do TFs bind dsDNA?
in the major groove they recognize target base sequences and bind to them
they dimerize and bind to palindromes in the major groove
DNA palindrome
5’ GAATTC 3’
3 ‘CTTAAG 5’
mammals have how many TF proteins?
2500
it takes a lot of genes to control a lot of genes
does each TF have its own transcription unit?
yes
leucine zipper
two crossed helices holding DNA
how far away can control sites in DNA be from the gene they control?
up to 30,000 bases away and sometimes even farther
