LECTURE 12 (Quantitative Loci) Flashcards
(38 cards)
What’s quantitative genetics?
traits that are more complex than monogenic or oligogenic because they have environmental component as well
The phenotypes are determined by which two things?
environmental variation and phenotypic variation
What are the main types of traits?
- 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)
What are quantitative traits determined by?
many genes that act independently (not related) + environmental effects
Can the phenotype/ genotype be predicted with quantitative traits?
no, because the environment has an effect on them.
what’s quantitative genetics?
the study of quantitative traits which are continuously varying characters
What does the polygenic theory involves?
it states that certain traits are produced due to the cumulative effect of several genes (assumes that genes are additive)
what if environmental variation is added to polygenic theory?
then we start to see much more variation of phenotypes
what states the number of phenotypes in the polygenic theory?
the genes
pheny= 2n + 1 being n the number of genes acting
give an example of polygenic inheritance of traits.
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
What are the two parameters that describe normal distribution?
- standard deviation and variance.
What are the main components of phenotypic variation in quantitative traits?
Vp= Ve (environmental) + Vg (genotipic)
how can we calculate Ve or Vg?
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
What are the main components of genotypic variation?
Va: additive variation
Vd: dominance genetic variance
Vi: epistatic or interaction genetic variance.
What’s additive variation? (Va)
sum of phenotypic effects of alleles when assembled in the genotype
what do we inherit from parents, alleles or genotypes?
WE INHERIT ALLELES
what is the dominance genetic variance (Vd)?
it’s the deviation from the genotypic values due to additive gene action due to dominance (dominance of one genes over other)
what is the epistatic or interaction genetic variance (Vi)?
the deviation from the genotypic values due to additive gene action between loci
What are the main components of environmental variation?
- unkonw causes
- spatial (env space)
- temporal (time)
- maternal (e.g nutrition)
is the genotype independent from the environment?
no, GXE INTERACTION.
explain the three types of gene environment interaction.
paper: 5 groups of varying level of a trait different categories of env. - additive: no G-env interaction - fan-shaped - cross-over.
what’s phenotypic plasticity?
phenotypic variation due to genotypic variation in response to the environment
with the example of drosophila from the lecture, explain the effect of N.S on different traits and why is that.
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.
what is broad sense heritability?
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
