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49 Cards in this Set
- Front
- Back
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variance
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exists in EVERY population, based on:
1. number of genes 2. environmental influence |
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continuous expression
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-single curve, phenotypes vary continuously between extremes
-ex: human height -genetic basis of inheritance harder to discern |
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discontinuous (discrete) expression
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-multiple peaks and valleys
-distinct phenotypic classes |
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V(phenotype)
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V(pheno) = V(geno) + V(enviro)
[nature vs nurture] |
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*Additive Alleles
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traits with incomplete dominance
-intermediate phenotypes (pink) |
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Heritability
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proportion of total phenotypic variance in a population that is due to genetic factors
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How does an additive allele differ from a non-additive allele?
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???
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Multiple Gene Hypothesis
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alleles of more than one gene contribute to determination of a phenotype
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# phenotypic classes
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2n + 1
where n = # of additive alleles, or # of genes |
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Ex: # phenotypic classes
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Given AaBBcc, how many phenotypic classes?
# pheno = 2(3) +1 = 7 |
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# genes (based on # pheno)
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# genes = (# pheno - 1)/2
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# genes (based on frequency)
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# genes = log(f(parental class))/-0.6
ALWAYS USE WHOLE NUMBERS |
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larger number of genes...
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more continuous variance
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mean
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average of class variance (vertical)
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variance
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stretch of distribution (horizontal)
-narrow dist = small variance -wide dist = large variance |
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traits strongly selected by nature...
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have LOW heritability because they have already been selected for
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broad sense heritability
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H^2 = 1 --> all V based on genes
H^2 = 0 --> all V based on enviro |
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selective differential
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Pop(avg) - Po(avg)
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narrow sense heritability
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0 < h^2 < 1
Pop(avg) - F1(avg)/ Pop(avg) - Po(avg) |
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if variance is based solely on genetics...
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selective breeding is possible
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if variance is based solely on environment...
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selective breeding is useless
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additive variance
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selectable
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dominance variance
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non-selectable
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if h^2 = 0...
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trait is NOT selectable
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eventually selection levels off...
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because eventually all individuals are homozygous (no more genetic variation)
h^2 = 0 |
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monozygotic twins
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genetically identical
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dizygotic twins
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fraternal - share 1/2 of genes (like siblings)
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concordant trait
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shared by both twins
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discordant trait
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not shared
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determining heritability via concordance
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if concordance MZ > DZ:
suggests that trait is heritable |
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heritability applies to...
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SPECIFIC POPULATION,
NOT individuals, NOT universal |
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even if heritability = 1
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enviro can significantly affect traits (i.e. effects of hunger on height during Great Depression)
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T/F: Most ag populations are NOT in Hardy-Weinberg.
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TRUE
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T/F: Most natural (non-ag) populations are highly inbre, and have little genetic diversity.
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FALSE
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T/F: Organisms in nature produce MORE offspring than the environment can support.
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TRUE
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T/F: Inbreeding alone causes homozygosity in a population.
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TRUE
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T/F: Horses and donkeys are considered to be reproductively isolated.
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TRUE
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T/F: Ex of allopatric speciation is when a population becomes divided by a geographic feature such as a mountain or large river.
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TRUE
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T/F: Heritability (H2 and h2) is a measure of the proportion of the total phenotypic variation of a given trait that is due to some aspect of genetic variability.
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TRUE
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STABILIZING selection occurs when...
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the greater viability of "average sized" newborns, relative to small or large newborns
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DIRECTIONAL selection occurs when...
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a population which is long-nosed individuals are preferred mating partners,
a population where male deer with large antlers are preferentially killed by hunters |
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If a trait is controlled by 4 genes, what portion of the F2 progeny will be as large/small as the parental?
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(1/4)^4 = 1/256
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6 genes control a trait, how many (phenotypic) classes are there?
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2(6) + 1 = 13
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Females selecting males based on large quantity of beer drinking...
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NOT in H-W equilibrium
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V(pheno) =
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Vp = Vg + Ve
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H^2 (broad sense)
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H^2 = Vg/Vp
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h^2 (narrow sense)
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h^2 = Va/Vp
a = additive alleles |
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If Vp = 50, Ve = 40, what is H^2?
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Vp = Vg + Ve
50 = x + 40 x = 10 H^2 = Vg/Vp x = 10/50 x = 0.2 |
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genetic drift
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when allelic frequencies fluctuate considerably in small populations
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