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Flashcards in Quantitative Genetics Deck (22)
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1

What is a difference between population genetics and quantitative genetics

Population genetics: discontinuous traits
Quantitative genetics: no discrete classes ie continuous distribution of phenotypes

2

Examples of quantitative traits

Length and weight
Behaviour
Fecundity
In fact, most LH traits
Most fitness traits
Colour pattern of guppies

3

What is the equation for phenotypic variation

Phenotypic variation = Genetic variation + Environmental variation
Vp = Vg + Ve

4

What are quantitative traits controlled by

multiple genes (i.e. polygenic)

5

what is the equation showing the relationship between no. of genes and no. of genotypes

N genes =3^N genotypes

6

Why are the metric effects of alleles not always easy to add up

If there is a dominant allele ie the phenotypic effect of a is masked by A

7

What are the issues with the studying quantitative variation with molecular markers?

Markers do not reflect environmental variation
They only poorly reflect non-additive variation
Markers are single locus, most traits multi-locus

8

What is broad sense heritability

Ratio of total genetic variance : phenotypic variance
H2 = VG/VP

9

(heritability) why can not all genetic variation be selected

because of dominance and epistatic variance

10

What is narrow sense heritability

Ratio of additive genetic variance : phenotypic variance
h2 = VA/VP

11

What does h^2 determine

determines how well population can adapt

12

What are the important points to remember when talking about heritability (h^2) and populations

The heritability estimate is specific to the population and environment you are analysing
The estimate is a population, not an individual parameter

13

What does h^2 no indicate

Heritability does not indicate the degree to which a trait is genetic
Rather, it measures the proportion of the phenotypic variance of a trait that is the result of genetic factors

14

What does T stand for

T is mean phenotypic value of the population

15

What does Ts stand for

Ts is the mean value of the selected parents

16

What does S stand for

S is called the selection differential

17

What is the symbol for the 'response to selection'

R

18

What is R and it's equation

R is the difference in mean phenotype of the parental and offspring generation
R=T'-T

19

What is the equation for adaptive response

Adaptive response = strength of selection (S) x heritability (h^2

20

How can a really uncommon recessive allele can contribute to a selective response

It it increases in frequency
After a population bottleneck
Founder event
Inbreeding

21

What hides a populations phenotypic variation, and how can it be released

dominance and epistatic variance, which can be released through bottle necks by increasing the chance of recessive alleles being displayed

22

If heritability of a selected trait is 0, what is selective response e.g large body size

0, even if only large organisms get to reproduce, there size is completely dependent on environmental variation, therefore there will be no change in size in their offspring