Week 1 - Genetic Change & Its Consequences Flashcards
What is a mutation and how are they categorised?
- genetic changes that can cause a disease
- they can be inherited by germline mutation or acquired by somatic mutation
- they can be silent or functional
- can be neutral, favourable, and non-favourable
What are chromosomes aberrations?
- chromosome defects that are either structural or numerical
structural: translocation, inversion, insertion, duplication, amplification, deletion
numerical: loss/gain of whole chromosome or its set
What are the types of point mutation?
silent: no change to the code
missense: one amino acid to another
nonsense: amino acid to stop codon
What is the effect of a nonsense mutation?
- it created a truncated protein, which is a protein shorter than its full-length version due to a premature stop codon
- this protein can interact with normal proteins
What types of mutations are there (specific to the change in the amino acid sequence)?
point mutation: change in a singular gene
frameshift: disrupting the triplet code
splicing: affecting splice sites (introns & exons)
regulatory: affecting the promoter or other regions causing an aberrant (unusual) expression
What are the effects of mutations in non-coding regions?
promoter: rate of gene transcription
regulatory region / operator site: gene regulation failure
UTR: disruption to mRNA translation / stability
splice sites: disrupted pre-RNA splicing
t/micro/long noncoding RNAs: dysfunctional gene regulation
What are the types of amino acid replacements?
conservative replacement: exchanged amino acids have similar properties and rarely cause protein dysfunction
radical (non-conservative): different properties causing pathogenic changes
What is haploinsufficiency?
- when one copy of the gene has been inactivated by a mutation
- the other copy has a reduced expressions so it is insufficient to fulfill its function
- OR it makes 50% of the product but it is not enough
What is transversion and transition mutation?
- transition is when a point mutation changes a purine nucleotide to another purine nucleotide or pyrimidine to another pyrimidine
- transversion is when the purine becomes a pyrimidine or vice versa
What is the rule for chromosome nomenclature?
- chromosome number
- short (p) / long arm (q)
- region
- band
decimal point - sub-band
How are cells prepared for karyotyping?
- cells are collected from either lymphocytes, skin, or amniocytes
- cultured
- arrested in metaphase using colchicine
- lysed with hypotonic saline
- mounted
- fixed
- stained with giemsa stain
- converted into ideograms for better visualisation
Why do dominant-negative mutations happen?
proteins often act as a part of a network by binding to each other and forming dimers/ multimers
How is BRCA1 and 2 an example of antagonistic pleiotropy?
- they increase cancer risk and tumour development, thus decreasing a person’s chance of survival but they also increase women’s fertility
- a positive and negative effect
What are the different types of centromere positions?
metacentric: in the middle
submetacentric: shifted away from the middle
acrocentric: near the end - short arms form satellites
telocentric (only in mice): at the very end
What is pleiotropy?
when one gene influences two or more phenotypic traits that can be unrelated
