8.2.2 Regulation Of Transcription And Translation Flashcards
(12 cards)
What are transcription factors
Proteins which regulate (stimulate or inhibit) transcription of a specific target gene in eukaryotes
By binding to specific DNA base sequences on a promoter regions
How are they used
Transcription factors move from cytoplasm to nucleus
They bind to DNA at a specific base sequence on a promoter region
This stimulates of inhibits transcription by helping or preventing RNA polymerase binding
How does oestrogen affect transcription
It’s lipid soluble steroid hormone so diffuses into cells
In cytoplasm it binds to its receptor, an inactive transcription factor forming an oestrogen-receptor complex
This changes the shape of the transcription factor forming an active transcription factor
This complex diffuses from the cytoplasm into the nucleus
Then it binds to a specific DNA base sequence on the promoter region of a target gene
Stimulating transcription of target genes by forming mRNA by helping RNA polymerase bind
Why does oestrogen only affect target cells
Other cells don’t have oestrogen receptors
What is epigenetics
Heritable changes in a gene function/ expression without changes to the DNA base sequence
Doused by changes in environment (diet, stress)
What is epigenome
Chemical modification of DNA and Justine proteins - methyl groups on DNA and acetyl groups on histones
Epigenetic control of gene expression
Methylation of DNA:
-to inhibit transcription it is increase
-to allow transcription it is decreased
Acetylation of DNA:
-to inhibit its decreased
- to allow its increased
How does methylation inhibit
Increased methylation of DNA-methyl groups added to cytosine bases in DNA
So nucleosomes pack more tightly together
Preventing transcription factors and RNA polymerase binding to promoter
How can acetylation inhibit
Decrease acetylation of histones, increased positive chance of histones
So they bind DNA more tightly
Preventing transcription factors and RNA polymerase binding to promoter
Relevance of epigenetics
Environmental factors (stress and diet) can lead to changes in epidemics
These can stimulate or inhibit certain genes that can lead to disease:
- increased M or decreased A inhibits
-decreased M or increased A stimulates
Diagnostic test can be developed that detect epigenetic changes before symptoms present
Drugs can be used to reverse epigenetic changes
What is RNA interference (RNAi)
Inhibition of translation of mRNA produce from target genes by RNA molecules
This inhibits expressions of a target gene
Regulation of translation by RNAi
Small RNAi(sRNAi) or micro RANi (mRNAi) binds to a protein, forming a RNA-induced silencing complex:
-sRNAi synthesised as a doubles strand (1 stand is incorporated)
-miRNA double strand (both strands incorporated)
Single stranded miRNA/siRNA binds to target mRNA with a complementary base sequence
Leads to hydrolysis or mRNA which is then degraded or prevents ribosomes binding
Reducing/preventing translation
