Gene expression Flashcards
What is a stem cell?
Undifferentiated/unspecialised cell
Define the term totipotent
Stem cells can differentiate into any cell type
Define the term pluripotent
Stem cells that can make all cell types except extra embryonic tissue
Define the term multipotent
Stem cells that can only produce a certain cell
How are IPS stem cells produced?
Turning adult cells into pluripotent cells using transcription factors
What is the role of oestrogen in gene expression?
Oestrogen enters the cell and binds to transcription factor
How are siRNA made?
A double stranded RNA molecules is cut into small sections, made single stranded and combined with RISC enzyme
How do siRNA function?
Complementary to mRNA. They then cut up the molecule so translation cannot occur
What is a transcription factor?
Controls the expression or transcription of genes
What type of transcription factor prevents transcription?
Repressors
What is a processing body?
Where an mRNA is degraded after being broken into fragments by associated proteins. miRNAs can be stored here to be transcribed at another time
What is epigenetics?
Heritable changes in gene expression without changing the DNA sequence caused by the environment
How does chromosomes being condensed affect gene expression?
Reduces transcription as transcription factors cannot reach the DNA and therefore the promoter
How does loosening chromosomes affect gene expression?
Increases transcription as transcription factors can now bind to the promoter region of DNA
What affect does increased DNA methylation have?
Deceases gene expression. Also, causes chromosome condensation
What affect does decreases acetylation have?
Less acetyl groups mean increases positive charges on the histones so they are more attracted to the negative DNA resulting in increased condensing of DNA and reduced gene expression
What is a mutation?
A change to the DNA Base sequence
What is the difference between substitution and deletion mutations?
A substitution is the replacement of one base for another whereas a deletion involves the removal of a base, resulting in a frame shift
Why is a deletion mutation more dangerous?
Causes a frame shift and causes all triplet codes after the mutation to change resulting in different amino acids and the protein not being produced.
Why can some substitution mutations be silent?
The new triplet code codes for the same amino acid due to the genetic code being degenerate
What is cancer?
Uncontrolled cell division
What is the difference between a malign tumour and a benign tumour?
Malignant grow faster, can metastasize, have whole body effects and requires surgery
What two genes control cell division?
Proto-oncogenes and tumour suppressor genes
What affect do tumour suppresser genes have?
Inhibits cell division by producing a protein that inhibits it
What affect do proto-oncogenes have?
Produce a protein/growth factor that stimulates cell divison
How can a mutation to a proto-oncogene cause cancer?
A mutation can lead it to constantly be expressed and so constantly producing the growth factor that stimulates cell division
How can a mutation to a tumour suppressor gene cause cancer?
Mutation leads to loss of protein that inhibits cell division resulting in uncontrolled cell division
How could methylation cause cancer?
Increased methylation of tumour suppressor genes leading to inhibition of TSG leading to loss of protein that stops cell division.
What is a frameshift?
A shift in the base triplets that follow on from the mutation
What are the environmental risk factors for cancer?
- Increased alcohol consumption
- High fat diet
- Smoking
- Viruses
- Exposure to radiation
- Dangers in the workplace
If a person has a mutated BRCA1 gene, what preventative measures can be carried out?
Mastectomy or increased screening for tumour formation
What is a colonoscopy?
Inserting a camera into the colon. Can be used to screen for tumour formation
How can gene therapy treat cancer?
A faulty allele can be replaced by a functioning allele and this will hopefully stop tumour growth
What is a phenotype?
Characteristics a person expresses
How can overeating be caused be genetic and environmental factors?
Environment- High food availability
Genetics- People having lower dopamine receptors
What is a twin study?
Studying identical twins to determine whether something is due to environmental or genetic factors
Why is a large sample size important?
More representative of the population
Give an example of where a twin study has been used
Alzheimer’s disease. Found that sometimes both identical twins didn’t develop the disease so there must be some environmental factors
