8A Regulation of Transcription and Translation Flashcards
Define transcription
When a gene is copied from DNA into messenger RNA using RNA polymerase
Do all cells carry the same genes
Yes
Why are different proteins made
Because different genes are expressed
What is different in cells with regards to genes
Their structure and function
What are transcription factors
Proteins which control the rate of transcription
Where do transcription factors move from
Cytoplasm to the nucleus
What to transcription factors bind to in the nucleus
Specific DNA sites near the start of the target gene
What do transcription factors called activators do
They stimulate the rate of transcription by helping RNA polymerase bind to the start of the target gene and activate transcription
What do transcription factors called represses do
They inhibit the rate of transcription the bind to the start of the target gene preventing RNA polymerase
What type of hormone is oestrogen
A steroid hormone
How does oestrogen affect transcription
It binds to a transcription factor called an oestrogen- oestrogen receptor complex
Where do the oestrogen- oestrogen receptor complex move to
Nucleus from the cytoplasm where it binds to specific DNA sites at the start of the target gene
What can the oestrogen- oestrogen receptor complex bind to
An activator helping RNA polymerase to bind to the start of the target gene
What does RNA interference do
inhibit the transcription of mRNA
Stage 1 of siRNA and miRNA in plants
once mRNA has been transcribed it leaves the nucleus for the cytoplasm
Stage 2 of siRNA and miRNA in plants
in the cytoplasm double stranded siRNA associates with several proteins and unwinds a single strand then binds to the target mRNA the base sequence of the siRNA is complementary to the base sequence in sections of the target mRNA
Stage 3 of siRNA and miRNA in plants
The protein associated with the siRNA cut the mRNA into fragments so it can no longer be translated the fragments then move into a processing body which contains tools to degrade them
Stage 1 of miRNA in mammals
in mammals the miRNA isn’t usually fully complementary to the target mRNA so it is less specific than siRNA and so it may bind to more than one mRNA molecule
Stage 2 of miRNA in mammals
it associates with proteins and binds to target mRNA in the cytoplasm
Stage 3 of miRNA in mammals
the miRNA complex physically blocks the translation of the target mRNA
Stage 4 of miRNA in mammals
The mRNA is moved into a processing body where it can either be stored or degraded
When it’s stored it can be stored or returned at another time
