Lectures 9 & 10, Genetic Variation Flashcards
What is the phenotype?
The interaction of the genotype with the environment.
How is variation presented in our DNA?
Single nucleotide polymorphisms and variable tandem repeats.
What are the three main types of mutation?
Base substitution, deletions and insertions
What is a base substitution?
The replacement of a base, usually a single base.
How is variation caused within a population?
Mutation
T/F: new alleles are caused by mutation?
True
T/F: Germ cell mutations are not as detrimental as somatic cell mutation
False
Why are germ cell mutations more detrimental than somatic cell mutations?
Germ cell mutations can be passed down generations, and also cells in the germ line are haploid, so there is a greater risk that the mutation will occur in a gene and not be fixed via excision repair for example
How can single base substitutions alter RNA splicing?
The substitution may occur within a coding exon.
What are synonymous mutations?
Substitution results in a new codon but specifying the same amino acid due to the generative nature of the DNA code
What is wobble?
Wobble is degenerative nature of the triplet codon-amino acid code where base substitution does not result in a different amino acid being produced.
What is the most common type of wobble? Give an example of an amino acid which exhibits third base wobble.
Third base wobble; valine
What is a nonsense mutation?
This occurs where a codon specifying an amino acid is replaced by a stop codon. Example: Try = UAU and UAC but the third base can be replaced to an A or G creating a stop codon
What are missense conservative substitution mutations?
This is where there is a replacement of an amino acid by another although they are chemically similar, thus having a minimal effect on protein function as the side chain of the new amino acid may be similar to that of the amino acid which was replaced.
What is non-conservative substitutions?
Where the replacement of one amino acid by another with a dissimilar side chain. Charge differences may be introduced and there may be replacement of polar side chains by non-polar side chains (vice versa).
How many polypeptide subunits are there in haemoglobin?
4
what type of protein is it?
Globular and tetrameric
Which chromosomes encode the alpha chains and how many of them are there?
Alpha chromosomes are encoded by genes chromosome 16; two chains
Where are the genes for the two beta chains?
On chromosome 11
How can haemoglobin disorders be characterised?
Two groups; structural abnormalities and the thalassemias
Give an example of a structural haemoglobin disorder
Sickle-cell anaemia
Describe the pathophysiology of a thalassemia
Where the two alpha and two beta chains of haemoglobin are structurally normal but they are reduced in quantity
How are the thalassemias classified?
They are named after which ever polypeptide (alpha or beta) is reduced in quantity.
