Chapter 8 Gene Expression Flashcards
Five Levels at which gene regulation occurs
1- epigenetic level 2- transcription level 3- mRNA processing level 4- translation level 5- post translation level
1- epigenetic level
Heterochromatin or euchromatin
DNA methylation
2- transcription level
Regulation by transcription factors ( rate of transcription )interplays with epigenetic level control
3- MRNA processing and alternative splicing
Different mRNA made from a give gene
4- translation level
How much of the mRNA is made into protein
DNA METHYLATION - epignetic level
This is the methylation of cytosine by methyl transferase in a GC island
What does dna methylation do?
Methylation of dna reduces gene activity..making the gene silent
By
Blocking the access of protein needed fro transcription
Attracts enzymes that promote histone methylation and deacitylation
Resulting in transcription repression
Example of DNA methylation
X inactivation
When the DNA of x chromosome is extremely METHYLATED and the chromosome condenses into a tight mass of heterochromatin( Barr body)
In females, genes of extra X are never expressed in somatic cells
Barr body
Facultative heterochromatin
Can loosen during DNA rep so that same X chromosome is copied
Transcription- transcription level
Transcription factors bind to the major groove on the promotor (regulatory DNA sequence) by non covalent bond
This is a very specific and strong interaction- tf bind at a very specific location
One tf can regulate many genes
1 gene is regulated by many tf at different sites and at different time
How transcription is regulated
1- GTFs bind to the core promoter , required for the transcription of genes transcribed by the specific promotor
2- other TFs Like NF1 and SP1 bind to promotor proximal control element like CAAT OR GC
- they regulate the frequency of transcription
- also Methylated C at GC can inhibit the binding of tfs so the gene is transcriptionally inactive
3- specific tfs bind to distal promotors
- they control the gene from distance
They repress of activate the transcription of gene or regulate the rate of transcription
These specific tfs are usually specific to a gene or a grp of genes
Translation level - these combination of different genes contributes to how much of the gene is expressed.
How to find a gene of interest
Promoter specifies which gene is expressed
Make a fusion of that gene promoter and GFP and put it in a multicellular organism
When that specific gene is expressed GFP is also expressed lightning up the regions
How many chloroplast in one plant cell
50
Inputs of a dependent reaction
H2o and sunlight
Products of a dependent light reaction
Atp
Nadph
O2
