Lecture 2 (Gene Expression) Flashcards
Transcription in Prokaryotes
Initiation: RNA polymerase attached to promoter
Elongation: RNA polymerase moves across the gene and makes a version in RNA
Termination: RNA polymerase crosses the terminator and releases the DNA
Does RNA polymerase move upstream or downstream?
downstream
Transcription in Eukaryotes
Initiation: transcription factors bind to the promoter then RNA polymerase binds to the promoter
Elongation: RNA polymerase moves across the gene and makes a version in RNA
Termination: RNA polymerase crosses polyadenylation signal sequence and releases from DNA
Differences in Prokaryotic and Eukaryotic Transcription
- Prokaryotes do it in the cytosol, eukaryotes do it in the nucleus
- prokaryotes don’t have TF, eukaryotes do have TF
- prokaryotes make mRNA, eukaryotes make pre-mRNA
- for prokaryotes it ends when it crosses the terminator, for eukaryotes it ends when it crosses the polyadenylation sequence
- prokaryotes don’t have a TATA box, eukaryotes have a TATA box
similarities in translation for prokaryotes and eukaryotes
- both start at the promoter
- the RNA pol moves downstream
- both make a version of RNA
chromatin
term for DNA and histones
euchromatin
can alternate between being loosely or high condensed
when can a chromatin be read?
it is “on” when it is loosely condensed
heterochromatin
remains highly condensed
telomeres
DNA sequences at the end of eukaryotic chromosomes
Acetyl groups
Bind to tails of histones ( they attach to protein not DNA)
can transcription occur in unacetylated histones?
no
acetyl groups are added to histone tails and
open up the DNA
Methyl groups are attached to DNA and
condense the DNA
epigentics
Certain traumas can turn off genes or alter gene expression.
refers to occasions when gene expression is altered , but the nucleotide sequence of the gene stays the same
how do cells express different genes?
- altering exposure of the DNA
- w/ TF
What the extra middle step that only occurs in eukaryotes?
RNA processing
RNA processing
- Addition of 5’ cap
- Addition of poly a tail
- Removal of introns
Why does RNA processing occur?
- to remove introns
- to label and tag the mRNA as “ready”
- protects the mRNA
- helps bind to the ribosome
2 basic steps for gene expression in both prokaryotes and eukaryotes?
Transcription
Translation
central dogma
replication, transcription, translation.
The process by which DNA is converted to a functional product
3 sites of a large subunit
E: tRNA leaves
P: first tRNA (MET)
A: new tRNA comes in
where does translation occur in both prokaryotes and eukaryotes?
In the cytosol, specifically at a ribosome
Translation
using instructions in RNA to start making proteins
