8.2.2 Regulation of transcription and translation

What is a transcription factor

specialised proteins that regulate gene expression by binding to specific sequences

(in eukaryotes this can be stimulated or inhibited when specific factors move from cytoplasm into nucleus)

Role of transcription factors in gene expression

regulate gene expression by binding to specific sequences to turn gene expression on or off

Mechanism by which oestrogen is able to initiate transcription

Oestrogen is a lipid soluble so diffuses between phospholipids in cell surface membrane

Oestrogen binds with complementary shaped receptor on transcriptional factor in the cytoplasm

this changes the shape of DNA binding site on the transcriptional factor which now allows it to bind to DNA

TF moves into the nucleus and binds to a specific base sequence on the DNA which stimulates the binding of RNA polymerase and so transcription

What is epigenetics

The way in which environmental factors can cause heritable changes in gene function without changing the base sequence

What is the epigenome

DNA is wrapped around histones which are covered in chemical tags which forms a layer above our genome

How does the epigenome effect the DNA

Causes the DNA histone complex to be tightly packed or loosely packed

condensed genes cannot be transcribed as transcriptional factors cannot access the gene

loosely packed genes can be transcribed as transcriptional factors can access the gene

What epigenetic marker causes DNA to be tightly packed

Methly groups/methylation

What epigenetic marker causes DNA to be loosely packed

acetyl groups/acylation

how epigenetics can control/stop disease(for proto-oncogenes)

these genes stimulate cells to divide, a mutation in these genes can cause it to become an oncogene which is permanently activated therefore continues to divide.

treated with epigenetic markers can can inactivate them we can prevent these genes from causing continuous cell division

how epigenetics can control/stop disease (for tumour suppressor genes)

these genes code for proteins that slow down/stop cell division

if this was to become inactivated it could cause the cell to continuously divide uncontrollable, if treated with epigenetic markers to keep this gene activated then cell division would be slowed

what is RNA interference

Regulates protein synthesis

small pieces of RNA can shut down protein translation by binding to mRNA that code for translation

They can either bind to the mRNA or physically prevent ribosomes from continuing to synthesize by marking the mRNA for destruction

how does siRNA interfere with translation

double stranded RNA is cute into smaller sections(siRNA) one of the siRNA strands combines with an enzyme

siRNA guides the enzyme to an mRNA molecule by comp base paring with a section on the mRNA

The enzyme cutes the mRNA molecule into small sections, it can no longer be translated into a polypeptide