Fundamental Molecular Flashcards
What are mutations?
Mutations are changes in the genetic material of a cell.
Natural selection requires genetic differences to be passed on through…
Recombination
The rate of spontaneous mutation is low but not zero. How many mutations are there per human child?
There are roughly 200 new mutations per human child. These are known as de Novo mutations and are not found in either parent.
Where do de Novo mutations occur?
De Novo mutations occur in the germ line cells.
Which are more common: somatic or germ line mutations?
Somatic mutations are much more common but are not passed on to offspring.
DNA replication has a very low error rate and most errors are repaired. Any error not repaired leads to…
Net mutation
How may net mutation be increased?
Increasing rate of DNA damage which may be caused by radiation, reactive oxygen species and mutagens in burnt food, among others.
Why do most mutations have no effect on phenotype?
Most mutations land between exons (on introns).
What are silent mutations?
Silent mutations are base changes which do not affect the amino acid encoded.
What are missense mutations?
Missense mutations are base changes which change the amino acid being coded. They may be conservative or non conservative depending on the similarity of the new amino acid to the original.
What are nonsense mutations?
Nonsense mutations are base changes which lead to a stop codon being encoded.
What are frameshift mutations?
Frameshift mutations can be insertions or deletions of base pairs. They act like nonsense mutations.
Why do most mutations which fall on important regions still have no effect?
They are recessive, and recessive mutations require a level of inbreeding to affect phenotype.
What causes Huntington’s Disease?
An autosomal dominant mutation which affects the HTT gene which codes for the Huntingtin. The mutant allele causes the CAG repeat to get longer (expanded microsatellite).
What are orthologs?
Orthologs are genes separated by speciation which have similar, or the same, function.
What are paralogs?
Paralogs are genes separated by duplication events and usually have diverged function.
What are Variable Numbers of Tandem Repeats and how are they categorised?
VNTRs are repetitive pieces of DNA which can be categorised as either microsatellites (1bp-9bp repeating) or minisatellites (10bp-100bp repeating).
What are Copy Number Variants?
CNVs are variations in the number of copies of a specific DNA segment on a chromosome between different individuals.
Point mutations and variations are known as variations if they have an allele frequency of <1%. What are they known as if the allele frequency is >1%?
Polymorphism
SNPs are classed as rare if they have an allele frequency…
Between 1% and 4.9%
SNPs are classed as common if they have an allele frequency…
≥5%
For a given biallelic system, the Hardy-Weinberg equation predicts what?
The genotype frequencies in the population which keep the allele frequency constant from one generation to the next.
The Hardy-Weinberg equation assumes the population…
Obeys random mating, is homogeneous, has not recently been small, any mutation between alleles is occurring at very low frequency and natural selection is not occurring.
What does “p” represent in the Hardy-Weinberg equation?
Allele frequency of A
