Control of gene expression Flashcards
How are genes prevented from expressing themselves?
- Preventing transcription
- Breaking down mRNA before it can be translated
What are totipotent cells?
Are able to mature into any body cell, such as a fertilised egg. They differentiate and become specialised cells (plants also have these)
What are stem cells?
Undifferentiated dividing cells that occur in animal tissues and need to be constantly replaced
What can stem cells be used for?
Can be used to treat a variety of genetic disorders, such a sickle cell anaemia
Where can stem cells be found?
- Embryos, before the cells have differentiated
- Adult bone marrow
What is cell specialisation?
The result of the selective expression of certain genes of the full complement found in every cell. These cells can control which genes are expressed
How can hormones effect gene expression?
Oestrogen is able to switch on a gene and start transcription by combining with the receptor on the transcription factor, which releases an inhibitor molecule
What role does oestrogen play in gene expression?
- Oestrogen is lipid-soluble, can diffuse through cell surface membrane
- Once inside, combines with site on receptor molecule of transcription factor
- By combining with site, oestrogen changes shape of receptor molecule on TF
- TF can now enter nucleus through pore and combine with DNA
- Combination of TF with DNA stimulates transcription of gene that makes up that portion DNA
What is siRNA?
Small interfering RNA
What effect does siRNA have on gene expression?
- Enzyme cuts double-stranded molecules of RNA into smaller sections called siRNA
- One of two siRNA strands combines with enzyme
- siRNA molecule guides enzyme to messenger RNA by pairing bases with complementary ones on section of mRNA
- Once in position, enzyme cuts mRNA into smaller sections
- mRNA no longer able to be translated into polypeptide
- Gene not expressed
What are the benefits of siRNA?
- Used to identify the role of genes in a biological pathway
- Some diseases are caused by genes, so siRNA can block these genes so the disease is not expressed
