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GENETICS > LECTURE 12 (Quantitative Loci) > Flashcards

LECTURE 12 (Quantitative Loci) Flashcards

1
Q

What’s quantitative genetics?

A

traits that are more complex than monogenic or oligogenic because they have environmental component as well

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2
Q

The phenotypes are determined by which two things?

A

environmental variation and phenotypic variation

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3
Q

What are the main types of traits?

A
  • continuous e.g height, weight
  • non continuous ; meristic: countable e.g number of denticles in a drosophila larvae and threshold; either have it or don’t have it (if you don’t then you0re over the threshold)
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4
Q

What are quantitative traits determined by?

A

many genes that act independently (not related) + environmental effects

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5
Q

Can the phenotype/ genotype be predicted with quantitative traits?

A

no, because the environment has an effect on them.

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6
Q

what’s quantitative genetics?

A

the study of quantitative traits which are continuously varying characters

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7
Q

What does the polygenic theory involves?

A

it states that certain traits are produced due to the cumulative effect of several genes (assumes that genes are additive)

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8
Q

what if environmental variation is added to polygenic theory?

A

then we start to see much more variation of phenotypes

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9
Q

what states the number of phenotypes in the polygenic theory?

A

the genes

pheny= 2n + 1 being n the number of genes acting

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10
Q

give an example of polygenic inheritance of traits.

A

pigmentation in plants, if there’re two bialletlic genes A and B, there will be 5 phenotypes due to additive gene action. everything is based in units of color. big alleles contribute 2 + 1/4 and small contribute 1/4 of units of color
AaBa will have 5 units of color the phenotype is determined by the number of units of color

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11
Q

What are the two parameters that describe normal distribution?

A
  • standard deviation and variance.
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12
Q

What are the main components of phenotypic variation in quantitative traits?

A

Vp= Ve (environmental) + Vg (genotipic)

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13
Q

how can we calculate Ve or Vg?

A

we make the other one 0.
Ve: individuals of uniform genotypes (Vg) grow in different environments
Vg: individuals of the same environmental conditions show different genotypes

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14
Q

What are the main components of genotypic variation?

A

Va: additive variation
Vd: dominance genetic variance
Vi: epistatic or interaction genetic variance.

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15
Q

What’s additive variation? (Va)

A

sum of phenotypic effects of alleles when assembled in the genotype

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16
Q

what do we inherit from parents, alleles or genotypes?

A

WE INHERIT ALLELES

17
Q

what is the dominance genetic variance (Vd)?

A

it’s the deviation from the genotypic values due to additive gene action due to dominance (dominance of one genes over other)

18
Q

what is the epistatic or interaction genetic variance (Vi)?

A

the deviation from the genotypic values due to additive gene action between loci

19
Q

What are the main components of environmental variation?

A
  • unkonw causes
  • spatial (env space)
  • temporal (time)
  • maternal (e.g nutrition)
20
Q

is the genotype independent from the environment?

A

no, GXE INTERACTION.

21
Q

explain the three types of gene environment interaction.

A 
paper:
5 groups of varying level of a trait
different categories of env.
- additive: no G-env interaction
- fan-shaped
- cross-over.
22
Q

what’s phenotypic plasticity?

A

phenotypic variation due to genotypic variation in response to the environment

23
Q

with the example of drosophila from the lecture, explain the effect of N.S on different traits and why is that.

A

N.S acts on traits related to reproductive outputs e.g eggs and ovary , additive genetic variance is lower for these traits because because N.S will increase favorable alleles, the dominant ones so Vd and Vi are higher.

24
Q

what is broad sense heritability?

A

proportion of phenotypic variation attributable to genetic effects (variation in genotype)
e.g if 61% it means that 61% of the variation in phenotype is due to variation in genotype

25
Q

what is narrow sense heritability?

A

phenotypic variation attributable to the sum of phenotypic effects of alleles when assembled in genotypes

26
Q

How’s heritability measured?

A

it’s measured in a population not in one individual

it’s measured by comparing relatives and by artificial selection?

27
Q

What’s covariance?

A

when you compare different relatives and see the amount of gene they share.

28
Q

How’s covariance used to measure heritability?

A

looking at the strength of covariance look at the parents mid value and offspring mid value and compare those in relation to covariance. this can be done with different families and produce an scatterplot the slope of the line is the heritability if it’s done with only one parent the slope is half the heritability

29
Q

how can we test the relatedness between two individuals?

A

IBD: n (0.5)^i
n= number of routes
i= number of meiosis

30
Q

how can we know the number of routes?

A

you always need to go back to the most common ancestor.

31
Q

difference between monozygous and dizygous twins.

A

MZ: come from same egg share all genes
DZ: come from different eggs share half of the genes

32
Q

How can we test two twins for the presence absence of a disease?

A

use the concordance rate.

33
Q

What’s the concordance rate of twins?

A

CR: the P(that twins) will have certain characteristic both

34
Q

How does CR varies bt MZ and DZ twins?

A

MZ CR> DZ CR

35
Q

give an example of distinct CR of a disease

A

CF 100% CR MZ and 25% CR DZ

36
Q

how can we compare MZ AND DZ TWINS for continuous characters rather than non-continuos.

A

we use the correlation coefficient (r)

37
Q

How does r vary bt MZ and DZ twins?

A

Mz r> DZ r

38
Q

what’s the main problem with twin studies?

A

they never have exactly same env, teachers and parents treat them differently

GENETICS (17 decks)

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