Genetic Variation

What is a genetic bottelneck?

an event that drastically reduces the size of a population

Give three examples of genetic bottlneck events:

1) migration

2) disease

3) environmental change/ disaster

How many new mutations are found in each diploid genome (approx)?

70

True or false: the rate of mutations increases with paternal age

true

What are somatic mutations?

Mutations occurring in any other cell of the body other than the germ cells

True or false: somatic mutations are inheritable

false

True or false: germline mutations are inheritable

true

What are germline mutations?

Changes in egg or sperm cells that are then incorporated into the DNA of each body cell of the children produced

Give two examples of exogenous factors that cause genetic mutations:

1) radiation

2) chemicals

True or false: exogenous factors mainly cause mutations in somatic cells

true

Give four endogenous factors that cause genetic variation:

1) non-disjunction in meiosis causing aneuploidy

2) recombination (translocation)

3) DNA replication errors (mispaired bases and slippage)

4) inadequate DNA repair mechanisms

Give two examples of DNA repair mechanisms used to correct errors in genes:

1) mismatch repair

2) base excision

Give the two main (and broad) classes of variation:

1) variation that doesn't alter the number of nucleotides

2) variation that results in a net loss or gain of DNA sequence

Give two examples of mutations that don't alter the number of nucleotides in the genome:

1) single nucleotide variations

2) balanced translocations and variations

What is a neutral variation?

DNA changes that are small scale and have no obvious effect on phenotype

What is a single nucleotide polymorphism?

A single nucleotide substitution in DNA which can be seen in more than 1% of the population

What is a single nucleotide variation?

a variation of a single nucleotide with no limitations on frequency

What is the name given to the type of mutation that insertions and deletions come under?

indels

What percentage of all human genetic variation comes from SNPs?

90%

True or false: most SNPs are diallelic

true

What database gives all known SNPs an ID number?

dbSNP

What are intronic variations?

variations found between exons that do not affect the resulting protein directly but could affect the regulation of transcription or splicing

What is a missense mutation?

Point mutation in which a single nucleotide is changed, resulting in a codon that codes for a different amino acid

What is a nonsense mutation?

When a stop codon is formed prematurely due to a point mutation

What is a synonymous mutation?

a silent change where a codon is changed but the same amino acid is still encoded for

What are simple repeat mutations? (and give an example)

repeats of codons or sequences - Huntington's is caused by a CAG repeat

Give two examples of diseases caused by simple repeat mutations:

1) Huntington's

2) Fragile X syndrome

True or false: simple repeat mutations are subject to genetic anticipation

true

What are microsatellites?

repeat length polymorphisms that are not evenly distributed and are prone to slippage

What are copy mumber variants?

where sections of the genome are structurally increased or decreased

What is the size threshold for CNVs?

must be larger than 50 base pairs

Which two regions of chromosomes show are particularly high rate of CNV variation?

1) pericentromeric regions

2) subtelomeric regions

Where are pericentromeric regions found on chromosomes?

close to the centromere

What genes often flank CNVs?

low copy repeats

What are low copy repeats?

blocks of duplicated genomic sequence longer than 1000 base pairs

The deletion of a section in what chromosome causes DiGeorge Syndrome?

22

What was the name of the genetic project which sequenced pericentromeric, subtelomeric regions and short arms of acrocentric chromosomes?

Telomere to Telomere Consortium

Describe how negative selection governs variation:

mutations that are strongly deleterious will quickly be eliminated

Describe how selection reduced diversity governs variation:

positive selection of a gene variant takes place when natural selection favours a trait

Give an example of positive selection of a gene:

the AMY1A gene codes for amylase and was increasingly favoured as humans began to eat more starch

Why do African populations have more genetic diversity?

less genetic bottlenecking has taken place there