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BB10007 Genetics > Population and Quantitative Genetics > Flashcards

Population and Quantitative Genetics Flashcards

1
Q

How would you work out genotypic frequency?

A
  • no. of individuals with genotype / total no. of individuals
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2
Q

What is the Hardy Weinberg Model and what are the assumptions of it?

A

Genotypic/allele frequencies will remain same after single generations of random mating following assumptions:

  • large population
  • random mating
  • no mutations
  • no migration or immigration
  • no selection
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3
Q

Why is the HWM often wrong?

A

Non random mating can occur - (3 types)

1) Positive assortative mating - similar individuals mate with similar individuals
2) Neg assortative mating - diff with each other
3) Inbreeding - relatives with each other

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4
Q

What are the issues associated with inbreeding?

A
  • reduced fitness

- increases homozygosity

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5
Q

What are the causes of change in allele frequency?

A

1) Genetic drift - random changes in allele frequency ( error = 1/2N) - Bottleneck is an example of this: Drastic reduction in pop size, new pop isn’t representative of old one. Founder effects too.
2) Natural Selection - diff genotypes have diff fitness, leads to changes in allele freq as favours certain alleles
3) Migration - movement of alleles from one pop to another. Reduces genetic differences between populations.

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6
Q

What is fitness?

A

A measure of the average contribution to the next generation

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7
Q

What is overdominance?

A

Heterozygote has highest fitness, neither allele favoured.

- selection maintains both alleles

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8
Q

What is a meristic (countable) trait?

A
  • determined by multiple genetic and environmental factors and measured in whole numbers eg. animal litter size
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9
Q

What is Threshold traits?

A
  • measured by presence or absence

- e.g susceptibility to disease

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10
Q

Definition of Phenotypic variance

A
  • total amount of variation among individuals in some trait, caused by underlying components of variation.
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11
Q

Definition of Broad sense Heritability

A
  • proportion of phenotypic variation attributable to genetic differences between individuals
  • H2 = Vg / Vp
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12
Q

Definition of Narrow sense Heritability

A
  • proportion of phenotypic variation that contributes to the resemblance between parent and offspring (additive genetic variance)
  • H2 = AGV / Phenotypic V
  • measured by regulation
  • linear relationship between parent and offspring
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13
Q

What are the components of Phenotypic variation?

A
  • Genetic Variance ( VG)
  • Environmental Variance ( VE)
  • Genotypic-environmental interaction variance (VGE)

VP = VG + VE + VGE

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14
Q

What are the components of Genetic variation?

A

Heritable Variation - additive genetic variance ( VA)
Non heritable variation -
1) Dominance genetic variance (VD)
2) Gene interaction (epistatic) - VI

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15
Q

What is regression?

A
  • predicting the value of one variable if the value of other is given
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16
Q

What is regression coefficient?

A
  • represents the slope of the regression line, indicating how much one value changes on average per increase in the value of another variable.
  • flat line = zero heritability
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17
Q

What is linkage disequilibrium?

A
  • 2 loci A and B with alleles A/a and B/b
  • and Linkage EQ combos of alleles at A and B should be randomly assorted.
  • LINKAGE DISEQ occurs when there’s an association with alleles at diff loci. EG A found with B
  • coupling of A and B and a and b
  • repulsion of A and b and B and a
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18
Q

What removes linkage diseq?

A
  • recombination
19
Q

What is pleiotropy?

A
  • traits usually inherited together, a single locus / gene that affects the expression of multiple traits.
20
Q

What is Quantitative Trait Locis?

A
  • location of the genome that causes diff values of the trait in question
  • tests done using genetic markers
21
Q

What is the genome wide association?

A
  • identifies casual loci by testing whether groups with diff phenotypes have diff frequencies of alleles at locus
  • using a dense sequence data but also marker data
22
Q

What is additive genetic variance?

A
  • predicts resemblance between parents and offspring
23
Q

What are breeding values?

A
  • twice mean deviation of its progeny from the population mean phenotype
24
Q

What is biological evolution?

A
  • genetic changes in a group of organisms
25
Q

What is Anagenesis?

A
  • evolution taking place in a single group with the passing of time
26
Q

What is Cladogenesis?

A
  • Splitting of one lineage into two, 2 new species arise.
27
Q

What is the phenetic species concept towards what a species is?

A
  • Individuals or populations highly clustered in phenotype space - assign species boundaries from this
28
Q

What is the biological species concept towards what a species is?

A
  • gene flow between populations - assign species boundaries
29
Q

What is the Phylogenetic species concept towards what a species is?

A
  • species represent smallest set of organisms that share a common ancestor, can be distinguished from other such sets.
30
Q

What is Phylogeny?

A
  • representation of relationship between groups of organisms (lineages, populations or species)
31
Q

What are Rooted and Unrooted trees? (not actual roots in the ground)

A
  • rooted use a distantly related species to infer ancestral state ( an outgroup )
  • unrooted don’t have an outgroup, we know relationship between lineages but no ancestral relationship
32
Q

What is allopatric speciation?

A

caused by geographic isolation - no gene flow between two pops

33
Q

What is peripatric speciation?

A

when population peripheral to a main population

34
Q

What is parapatric speciation?

A

when populations aren’t isolated but adjoining - individuals mate locally

35
Q

What is sympatric speciation?

A

when populations overlap forming new species in middle

36
Q

2 Types of reproductive isolation

A

Prezygotic - don’t encounter each other, habitat isolation, temperal, behavioural, gametic incompatibility which stops a zygote forming

Post zygotic - zygote dies, f1 hybrid inviable. f2 survive but sterile

37
Q

What is secondary contact?

A
  • lineages split but come back into contact, will the hybrids be viable?
38
Q

What are genetic markers?

A
  • they feature in the genome and allow us to differentiate between diff alleles
39
Q

What is forensic genetics?

A

match DNA samples to individual, family or species

40
Q

The word ‘haplotype’ means…

A

refers to a chromosome block inherited as a single unit

41
Q

Complex traits are…

A

Typically affected by many genetic and environmental factors

42
Q

Correlations between traits can be due to…

A
  • Pleiotropy
  • Linkage disequilibrium
  • Environmental effects
43
Q

What can increase variation between populations?

A

1) Mutation
2) Genetic drift
3) Natural selection

44
Q

Genetic markers are…

A

molecular variants used to differentiate between alleles

BB10007 Genetics (3 decks)

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