Gene Expression- Regulation of Transcription and Translation Flashcards
What is transcription?
When a gene is copied from DNA into mRNA
What is RNA polymerase?
The enzyme responsible for synthesising mRNA from DNA
How are all cells similar and how do they differ?
All cells carry the same genes but the structure and function of different cells varies
Why does the structure and function of different cells vary?
Because not all genes in a cell are expressed
What happens because different genes are expressed?
Different proteins are made and these proteins modify the cell- determine cell structure and cell processes
What controls transcription of genes?
Transcription factors
How do transcription factors move in eukaryotes?
From the cytoplasm to the nucleus
What happens to transcription factors in the nucleus?
Bind to specific DNA sites near the site of their target genes
What are target genes?
The genes transcription factors control the expression of
How do transcription factors control expression?
By controlling the rate of transcription
What do activators (a type of transcription factor) do?
Stimulate or increase the rate of transcription by helping RNA polymerase bind to the start of the target gene to activate transcription
What do repressors (a type of transcription factor) do?
Inhibit or decrease the rate of transcription by binding to the start of the target gene which prevents RNA polymerase from binding to stop transcription
How can the expression of genes also be affected?
By other molecules in the cell such as oestrogen
What is oestrogen?
A steroid hormone that can affect transcription by binding to a transcription factor called an oestrogen receptor, forming an oestrogen-oestrogen receptor complex
How does the oestrogen-oestrogen receptor complex move?
From the cytoplasm into the nucleus where it binds to specific DNA sites near the start of the target gene
How can the oestrogen-oestrogen receptor complex act?
As an activator of transcription
What is gene expression also affected by in eukaryotes?
RNA interference
What is RNA interference?
Where small double-stranded RNA molecules stop mRNA from target genes being translated into proteins
What molecules are involved in RNA interference?
siRNA (small interfering RNA) and miRNA (micro RNA)
What happens once mRNA has been transcribed?
It leaves the nucleus for the cytoplasm
What happens in the cytoplasm?
Double-stranded siRNA associates with several proteins and unwinds- a single strand then binds to the target mRNA- base sequence of siRNA is complementary to the base sequence in sections of the target mRNA
What is the role of the proteins associated with the siRNA?
They cut the mRNA into fragments so it can no longer be translated and fragments then move into a processing body which contains ‘tools’ to degrade them
