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Y2 EMS- Theme 2- Genetic And Environmental Causes Of Disease > 6. Normal Genetic Variation > Flashcards

6. Normal Genetic Variation Flashcards

1
Q

What can reduce diversity

A

Genetic bottlenecks

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2
Q

What is a genetic bottleneck caused by

A

Speciation, migration, environment, disease

Reduction in population

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3
Q

What promotes diversity

A

Mutation

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4
Q

What is a mutagen

A

Agents that cause mutations eg, physical/ chemical

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5
Q

How can UV light cause melanoma

A

Too much UV light = causes pyrimidine dimers to form = abnormalities in subsequent replication

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6
Q

In what way do alkylating agents cause mutation

A

Transfer methyl/ ethyl to backbone phosphate = causes G to T

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7
Q

How many base pairs do we all have

A

3 x 10^9

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8
Q

What percent of human genome differs between people

A

0.1%

6 x 10^6 different base pairs

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9
Q

Which genetic testing technique can show frequency of mutations

A

WGS

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10
Q

What happens to the rate of germ line mutations with paternal age

A

Increases

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11
Q

Where is a germ line mutation present

A

Egg or sperm = heritable = all cells affected in offspring

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12
Q

Are somatic mutations inheritable and where do they occur

A

In non germ line tissues

Cannot be inherited

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13
Q

What are the two types of origins of genetic variation and give examples fir each

A
  • exogenous (eg, radiation, chemicals, mostly somatic)

- endogenous ( segregation/aneuploidys , recombination/trasnoclations, DNA replication errors, inadequate DNA repair

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14
Q

What types of mutations dont alter teh DNA content

A
  • Single nucleotide replacements

- balanced translocations/ inversions

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15
Q

What percentage of our DNA is poorly conserved

A

90%

Small DNA changes don’t always result in an obvious effect on phenotype

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16
Q

What is a SNP

A

Single nucleotide polymorphism = if a single nucleotide variation occurs in more than 1 % of population

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17
Q

What is the most common SNP

A

C —> T

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18
Q

Indel meaning

A

Insertion or deletion of one or more nucleotides

19
Q

What is a CNV

A

Large indels

Changes in copy number of sequences greater than 100 in length

20
Q

Are silent variations of SNPs more common

A

Yes

21
Q

What is minor allele frequency- MAF

A

The frequency of the less common variant in a population (of a SNP)

22
Q

What % of all human genome variation do SNPs make up

A

90%

23
Q

What is a diallelic SNP

A

When the base can change to one other base eg:

C —> T

24
Q

What is a triallleic SNP

A

When the base can change to two other bases eg,

C—> A or T

25
Q

What are Intronic/ intergenic variants

A
  • Variants that occur between genes/ exons

- dont affect protein directly

26
Q

Why can intronic variantions still be bad

A

Can affect the regulation of transcription/ splicing

27
Q

What are three types of coding ‘extronic’ variants

A
  • missense = nonsynmous = a.a change
  • nonsense = stop= change of a.a to stop codon = leads to truncation of protein
  • silent = synonymous = codon for a.a is changed but some same a.a still coded for, eg: GGC = Glycine and GGU = Glycine
28
Q

Which type of mutation leads to truncation of protein

A

Nonsense

29
Q

Which type of protein leads to the same amino acid being coded for

A

Silent

30
Q

What are SSRs

A

Simple repeat sequences/ micro satellites = repeated region of DNA = occur at thousands of locations on the gene
- unstable, prone to replication slippage

31
Q

What is genetic anticipation

A

When the repeat length of variant in a gene can increase in meiosis so the longer sequence is passed onto child = earlier onset in child

32
Q

What is microsatelltie DNA

A

A tract of repetitive DNA motifs are repeated, about 5 to 50 times

33
Q

Give 3 examples of a disease which is subject to genetic anticipation

A

Huntington’s disease
Fragile X syndrome
Spinocerebellar ataxia = progressive, degenerative involving loss of full control of bodily movements

34
Q

What does the CNV map show

A

Documents teh extent and characteristics of CNV among healthy populations

35
Q

Which regions of a chromosome show a particularly high rate of CNV variation

A
  • pericentromeric (near/ on each side of the centromere)

- subtelomeric (segments of DNA between telomeric caps and chromatin)

36
Q

Which genes are the least affected by CNVs

A

Genes that are associated with disease

37
Q

How many genes can be comepletly removed from the genome without producing apparent phenotypic consequences

A

More than 100

38
Q

Give an example of cells where CNVs are enriched n why

A

In cells involved in immune response - need to be diverse to respond to different pathogens etc

39
Q

What a percentage of teh human genome isn’t functionally restrained n generally permissive of variation

A

90%

40
Q

What are deleterious mutations eliminated by

A

Natural selection

Eg, mutations that compromise early dev/ neonatal health wont persist in population

41
Q

What is postive selection of CNVs

A

When a beneficial adaptation spreads

42
Q

What does teh human AMY1A gene code for n how is it an example of postive selection of CNVs

A
  • codes for salivary amylase which hydrolyses starch
  • people in populations with high starch diets have more copies of this AMY1A gene = spread as human diets became increasingly rich in insoluble starch
43
Q

What % of human genetic variation is found within populations

A

85 to 90%

44
Q

What % of human genetic variation is found between populations

A

Only 10 to 15%

Y2 EMS- Theme 2- Genetic And Environmental Causes Of Disease (7 decks)

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