Control of Gene Expression Flashcards
When might gene mutations take place?
During DNA replication.
DNA is vulnerable as it is single stranded.
Mistakes may take place in replication.
What happens in an addition gene mutation?
An extra nucleotide is added.
Causes a frame shift.
What happens in a deletion gene mutation?
A nucleotide is removed.
Causes a frame shift.
What happens in a substitution gene mutation?
A nucleotide is removed and another put in its place.
Does not cause a frame shift.
What is a stem cell?
Undifferentiated cells that can divide indefinitely and turn into other specialised cells.
Name four types of stem cell
Totipotent
Pluripotent
Multipotent
Unipotent
What is a totipotent stem cell?
An undifferentiated cells that can divide indefinitely and specialise into any type of cell
What is a pluripotent cell?
An undifferentiated cells that can divide indefinitely and specialise into a any cell type excluding the placenta and embryo
What is a multipotent cell?
An undifferentiated cells that can divide indefinitely and specialise into a few types of cell
What is a unipotent cell?
An undifferentiated cells that can divide indefinitely and specialise into only one type of cell
Give an example of a unipotent cell
Cardiomyocyte
which types of stem cell are found in embryos?
Totipotent and pluripotent cells
Give some uses of stem cells
Medical therapies eg bone marrow transplants to treat diseases like leukaemia
Drug testing on sheets of cells
Research on formation of organs and embryo
How are induced pluripotent stems cells produced?
From mature, specialised cells. The cells regains the ability to differentiate through the use of proteins in particularly transcription factors
What is a transcription factor?
A protein that controls the transcription of genes so that only certain parts of the DNA are expressed
Describe how a transcription factor work
TF moves from the cytoplasm into the nucleus
Bind to promoter region upstream of target gene
Inhibits or promotes the binding of RNA polymerase to the gene. This decreases or increases the rate of transcription
Name a hormone that influences the rate of transcription
Oestrogen
Describe how oestrogen influences the rate of transcription?
Simple diffusion through membrane into cell (steroid hormone)
Binds to a receptor on the transcription factor to form a hormone-receptor complex
Causes a change in shape of complex
Complex enters nucleus and acts as a transcription factor to inhibit or stimulate the binding of RNA polymerase to the gene
Define epigenetics.
A change in the expression of a gene without a change to the base sequence of DNA which can be inherited.
Name the epigenetic tag that can bind to histones
Acetyl groups
Name the epigenetic tag that can bind to cytosine bases on DNA
Methyl groups
How does increased methylation of DNA affect gene transcription?
Addition of methyl to cytosine bases
Prevents transcription factors from binding to the promoter
How does acetylation of histones affect gene transcription
Acetyl groups are positively charged.
When attached to histone they repel each other
The DNA is less tightly bound to the histone
Allows TF and RNA polymerase to access gene more easily
DNA that is tightly packed preventing transcription has been …..
silenced
What does your epigenome respond to?
Environment
Decreased gene expression is brought about by….
Decrease acetylation
Increased methylation
Increased gene expression is brought about by ….
Increased acetylation
Decreased methylation
Epigenetics has been associated with what type of disease?
Cancer
What type of molecule is involved in silencing mRNA?
siRNA
What happens to mRNA during RNA interference?
mRNA is cut up to prevent it being translated
Double stranded RNA is made and then hydrolysed to make short sections of double stranded RNA. Name the enzyme involved
Dicer
Once the siRNA is formed what does it bind to?
An enzyme
RISC
What is unique about the siRNA and the mRNA it is going to silence?
Base sequence is complementary
RNA interference to regulate gene expression is an example of ….
Post-transcriptional control
Transcription factors to regulate gene expression is an example of ….
Pre-transcriptional control
Name two genes that control cell division
Proto-oncogenes and tumour suppressor genes
What is the function of a proto-oncogene?
Stimulate cell division
What is the function of a tumour suppressor gene?
Slows down cell division
What would happen if a proto-oncogene is mutated?
Turn into an oncogene
Uncontrolled cell division
What would happen if there was a mutation in a tumour suppressor gene?
Uncontrolled cell division
Mutations in genes that control cell division cause …
Cancer
What are oncogenes?
Mutate proto-oncogenes
How do tumour suppressor genes work?
Slow down cell division or tells cells to die
What is apoptosis?
Programmed cell death
What is the consequence of a mutation in a tumour suppressor gene?
Stops inhibiting cell division
Cells divide out of control
Give a difference between a benign and malignant tumour
Benign tumours do not spread to other parts of the body
Cannot invade neighbouring tissues
Describe the role of tumour suppressor genes
Code for protein that control cell division
Stop the cell cycle when damage is detected
Involved in apoptosis - cell e=death
