19.2 Control Of Gene Expression

Question 1

What’s epigenetics

Answer 1

the study of gene expression control by DNA modification

Question 2

What causes cells to be specialised

Answer 2

their genes are switched on and off selectively which controls to proteins made and functions

Question 3

what are transcription factors

Answer 3

proteins that bind to the DNA and switch genes on or off by changing the rate of transcription

Question 4

What are the 4 methods of gene expression

Answer 4

1. transcriptional - genes can be turned on/off
2. post transcriptional 0 RNA processing
3. translational - translation can be stopped
4. post translational - proteins can be modified after synthesis

Question 5

What’s the process of (1) transcriptional gene expression

Answer 5

transcription factors control gene expression at transcriptional level;
this can be done by altering the rate of transcription of genes;

Question 6

What’s chromatin remodelling in (1) transcriptional gene expression

Answer 6

heterochromatin = tightly wound DNA; transcription not possible as RNA polymerase can't access the genes 
euchromatin = loosely wound DNA; can be freely transcribed 

simple way for cells to regulate type of proteins made

Question 7

What’s methylation (histone modification in (1) transcriptional gene expression)

Answer 7

DNA coils around histones because they’re + charged and DNA is - charged

Methylation of DNA & histones= nucleosomes pack tightly together; transcription factors bind to DNA, GENES AREN’T EXPRESSED; adding methyl groups makes histones more hydrophobic binding more tightly which prevents transcription; e.g. of repressor transcription factor

Question 8

What’s histone acetylation (histone modification in (1) transcriptional gene expression)

Answer 8

results in loose packing of nucleosomes; transcription factors can easily bind to DNA and GENES ARE EXPRESSED; by adding acetyl groups or phosphate groups, it reduces the + charge of the histone, causing DNA to unravel slightly; e.g. of activator transcription factor

Question 9

What’s the Lac operon in (1) transcriptional gene expression)

Answer 9

an operon is a section of DNA that contains a cluster of structural genes that are transcribed together and expressed at the same time. In prokaryotes