transcription

gene structure for prokaryotes or bacteria

operon

• structural gene

• operator

• promoter

• regulator

operon

the whole thing

structural gene

code for proteins

operator

gene turns on/off here

repressor is bound here

promoter

RNA polymerase will bind here

regulator

produces the repressor

if repressor is bound at the operator,

then the gene is off bc the operator cant turn it on

in the presence of lactose

the lac operon is on

without lactose,

lac operon is off

what does lac operon do

metabolize and break down lactose

Some bacteria is introduced into a glass of milk, what would be true regarding the lac operon?

• Is the repressor bound to lactose or bound to the DNA?

• is RNA polymerase II free to transcribe the gene or is it blocked?

• Can the bacteria metabolize lactose?

it is bound to lactose

it is transcribed to the genes

yes it can

are upstream elements close in sequential order? how bout 3D space?

not in sequential order but yes in 3D space

transcription factors

proteins that will increase transcription, and ability to bind

if there is heterochromatin, is there transcription

no there is none

if there is euchromatin, is ther transcription

there is some transcription ^

if there is euchromatin and transcription factors together, is there transcription

yes a lot ^^

if using an enhancer, would there be transcription

yes, it will help increase transcription ^^^

if using a super enhancer, would there be transcription

yes there would be the most transcription using this ^^^^

what are the three steps of transcription

initiation, elongation, termination

what is the goal of initiation

to bind RNA polymerase to promoter

TATA box

specific cite in motor region that RNA polymerase is binding to, but not if there is a mutation

what is the goal of elongation

to make mRNA

how does elongation occur

5’ to 3’, it is made 5’ to 3’, read 3’ to 5’

what is the template strand

3’ to 5’, how it is read

what is the goal of termination

to stop making mRNA

what is the stop sequence

AAUAAA

what is pre-mRNA

modifications made to mRNA

what is the product of transcription

pre-mRNA

can RNA polymerase start de novo

yes it can

what are the parts of post-transcriptional modification

5’ Cap, 3’ Poly-A Tail, Exons and Introns, Spliceosomes

what is 5’ cap

tells ribosomes to start here

what is 3’ poly-A tail

at very end, has a lot of AAAA

what are exons

coding DNA regions to make proteins

what are introns

non-coding DNA regions, aren’t fully necessary so spliced out

spliceosome

loop where intron is cut

splicing

introns are removed, exons are sliced and joined together

alternative slicing

allows creation of multiple protein in the same gene

where does post-transcriptional modifications occur

still in the nucleus

importance of post-transcriptional modifications

Protect Integrity of mRNA

Export of mRNA out of Nucleus

Ribosome Function