Quantitative Genetics Flashcards
What is a difference between population genetics and quantitative genetics
Population genetics: discontinuous traits
Quantitative genetics: no discrete classes ie continuous distribution of phenotypes
Examples of quantitative traits
Length and weight Behaviour Fecundity In fact, most LH traits Most fitness traits Colour pattern of guppies
What is the equation for phenotypic variation
Phenotypic variation = Genetic variation + Environmental variation
Vp = Vg + Ve
What are quantitative traits controlled by
multiple genes (i.e. polygenic)
what is the equation showing the relationship between no. of genes and no. of genotypes
N genes =3^N genotypes
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
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
What is broad sense heritability
Ratio of total genetic variance : phenotypic variance
H2 = VG/VP
(heritability) why can not all genetic variation be selected
because of dominance and epistatic variance
What is narrow sense heritability
Ratio of additive genetic variance : phenotypic variance
h2 = VA/VP
What does h^2 determine
determines how well population can adapt
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
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
What does T stand for
T is mean phenotypic value of the population
What does Ts stand for
Ts is the mean value of the selected parents
What does S stand for
S is called the selection differential
What is the symbol for the ‘response to selection’
R
What is R and it’s equation
R is the difference in mean phenotype of the parental and offspring generation
R=T’-T
What is the equation for adaptive response
Adaptive response = strength of selection (S) x heritability (h^2
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
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
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
