Genetics Flashcards
What is the premise of precision medicine?
It takes into account individual variability in genes, environment, and lifestyle for each person, so only the people who will benefit from the treatment will be given it.
What is the amount of protein produced determined by?
1) Rate of transcription (manufacture of Pre-mRNA)
2) Rate of splicing to mRNA
3) Half life of mRNA
4) Rate of processing of polypeptide
What are polymorphisms?
Any variation in the human genome that has a population frequency of greater than 1% or any variation in the human genome that does not cause a disease in its own right.
What are acrocentric chromosomes?
Chromosomes that only have a long arm
What does it mean to have a balanced chromosome rearrangement?
All the chromosomal material is present
What is an unbalanced chromosome rearrangement?
There is extra or missing chromosomal material. Usually 1 or 3 copies of some of the genome.
What is Aneuploidy?
Whole extra or missing chromosome.
What is a translocation?
The rearrangement of chromosomes
What are microdeletions?
Deletions too small to see at the chromosome level
What is a Robertsonian Translocation?
When two acrocentric chromosomes become stuck end to end.
Why is X chromosome aneuploidy better tolerated?
Because of x-inactivation
What does unbalanced translocations result in?
Miscarriage (when large segments are translocated) or a dysmorphic delayed child (when small segments are translocated).
What can molecular cytogenetics not detect?
Balanced chromosome rearrangements
Why does somatic mosaic occur?
Because all cells suffer mutations as they divide.
What can chromosome changes do that might cause cancer
Activate an oncogene or delete a tumour suppressor
Explain seven types of mutation
- Promotor Mutation- results in no or reduced transcription and in some cases no protein.
- Splice Consensus altered- results in different transcription and abnormal protein as introns may remain in the mature transcript.
- Nonsene Mutation- change in base results in a stop codon being coded for so transcription is terminated early.
- Missense Mutation- change in one base results in a different amino acid being coded for.
- Insertion- base is added which results in a frame shift mutation.
- Deletion- one bases or sections of code are deleted.
- Expansion- part of a code is repeated
What does it mean if an insertion or deletion is in frame?
The reading frame is not altered by the change i.e. the number of added or deleted nucleotides is divisible by three.
What is penetrance?
The likelihood of having a disease if you have a gene mutation.
Name and explain 3 types of mendelians inheritance
- Autosomal dominant (Mendelian)- if you get one copy of the abnormal gene you will get the disease.
- Autosomal recessive (Mendelian)- two copies of the abnormal gene must be present for the individual to get the disease.
- X-linked (Mendelian)- mutation of the X chromosome causes the disease, males more likely to be affected as only one X chromosome so cannot mask any abnormalities.
What is multifactorial inheritance?
Basically refers to everything that isn’t Mendelian inheritance, genetic contribution to any disease process.
What are copy number variations?
Extra or missing sections of genetic material.
Name four genes that are involved in cancer
Oncogenes
Tumour suppressors
DNA repair genes
Drug metabolism genes (that metabolise carcinogens)
Explain the difference between driver and passenger mutations
Driver mutations: mutations that drive carcinogenesis
Passenger mutations: incidental mutations that happen because the tumour is unstable
Explain DNA methylation is relation to cancer
- DNA Methylation is the addition of a methyl group that usually occurs on cytosine bases just before guanine bases. Methylation represses transcription of that gene, if that gene is a promotor then transcription will not happen.
- Methylation is an epigenetic modification, changes in the chemical structure but not the sequence.
- Methylation makes mutation (C to T) more likely
- Abnormalities of methylation cause genetic disease
- Methylation causes gene silencing in cancer
Explain Knudson’s “Two Hit” Hypothesis
- You can inherit a cancer disposition or get the same cancer through acquired mutations. Often you need two copies of gene for tumour to develop.
- Both genes could be affected by somatic mutation though or one copy may be inherited.
