7. Regulation Of Transcription And Translation Flashcards
What us transcription
When a gene coped from dna into messenger rna
Rna polymerase helps
Why are cells in different people have a different structure / function ?
BechSe not all genes in a cell are expressed - transcribed to make a protein
Because different genes are expressed and different proteins are made which can modify the cell
Proteins determine the cell structure and control the cells processes
What is the transcription of genes controlled by ?
Protein molecules called transcription factors
The role of transcription factors in eukaryotes ?
Move from cytoplasms to the nucleus
In nucleus they bind to specific DNA sites called promoters
Promoters found near the start of their target genes - the genes they control expression of.
The transcription factors control expression by controlling rate of transcription
What is the role of activators ?
Stimulate or increase rate of transcription eg help rna polymerase bind to start of target gene and activate transcription
What is the role of repressors ?
Inhibit or decrease rate of transcription eg bind to start of target gene, prevent rna polymerase from binding, stopping transcription
How does oestrogen affect transcription ?
It binds to a transcription factor called an oestrogen receptor which forms an oestrogen-oestrogen receptor
Complex
Complex moves from cytoplasm to nucleus where it binds to specific dna sites near starts of target gene
Complex can act as activator of transcription or even a repressor
Not all cells are affected by oestrogen , why?
Not all cells have oestrogen receptors
What are RNAi molecules ?
Small lengths of non-coding rna - they don’t code for proteins
How does RNAi affect gene expression in eukaryotes?
They stop mRNA from target genes being translated into proteins
Also happens in prokaryotes
What are the 2 molecules involved in RNAi?
siRNA - small interfering RNA
miRNA - micro rna
How many strands do siRNA and tRNA have ?
Double stranded
SiRNA and miRNA in plants
Once mRNA has been transcribed it leaves the nucleus for the cytoplasm
In cytoplasm double stranded siRNA associates with proteins and unwinds.
One of the resulting single strands of siRNA is selected and the other strand is degraded - broken down
Single strand of siRNA is completely to target mRNA so binds and proteins of siRNA cut mRNA into fragments can’t be translated - fragments then degraded
How could sIRNA have potential in treating genetic disorders ?
Stopping harmful gene from being expressed
If they’re complementary to mRNA they could be inserted into affected cells and bind to mRNA blocking translation of protein
miRNA in mammals
In mammals the miRNA isn’t fully complementary to mRNA so it’s less Specific than siRNA and it may target more than one mRNA molecule.
When first transcribed it exists as a long folded strand
Processes into 2 single strands by enzymes in cytoplasm
One of the strands associated with proteins binds to the target mRNA in cytoplasm and the miRNA protein compact physically blocks the translation of target mRNA
mRNA is then stored of degraded
If stored it can return later to try translation against
