7.2 Factors affecting gene expression Flashcards
1
Q
What are transcription factors
A
- Proteins which bind to DNA
2
Q
Explain how transcription factors work on promoter sequences
A
- Transcription factors bind to promoter sequences which is a signal for RNA polymerase to start synthesising a strand of mRNA
3
Q
Explain how TF work on enhancer regions
A
- TF binds to enhancer regions and changes chromatin structure. It can make it more open which allows for active gene expression or it close it by making it tighter, this is gene inactivity.
4
Q
Explain how RNA splicing works
A
1 - Pre mRNA is produced, which contains introns and exons.
2 - Spliceosomes cut out all introns, leaving only coding regions of mRNA
3 - Spliceosomes put the exons back together to form mature mRNA.
5
Q
How can RNA splicing lead to the different products from the same gene ?
A
- RNA splicing can join the same exons in different ways to produce different versions of the same RNA strand
6
Q
Explain what is meant by epigenetics
A
- Changes that affect gene expression
- Via DNA methylation or histone modification
- Which is involved in cell differentation
7
Q
What are three examples of epigenetic modification
A
- DNA Methylation
- Non-coding RNA
- Histone modification
8
Q
Explain how DNA methylation works
A
- Methyl group binds to CpG site which prevents transcription factors or RNA polymerase binding to promoter region, causing gene to be silenced
9
Q
What are the two forms of histone modification
A
- Acetylation
- Methylation
10
Q
How does DNA acetylation work
A
- Adding of acetyl group to histone tail which loosens nucleosomes wrapped around histones. RNA polymerase can access it easier.
11
Q
How does DNA methylation work in terms of histone modification
A
- Methyl group binds to histone tail which causes nucleosomes to be more tightly packed around histones, making the gene inaccessible to RNA polymerase.
12
Q
How is epigenetic modification important in cell differentiation
A
- As the organism grows, cells differentiates due to external and internal stimuli.
- This is mainly done by epigenetic changes, e.g different genes being expressed.
