G12

Question 1

what are inherited from parents?

Answer 1

alleles not genotypes

Question 2

what are the three trait types

Answer 2

continuous - bell curve
meristic - countable
threshold (multifactorial) - enviro and multiple genes

Question 3

what is continuous distribution due to?

Answer 3

polygenic variation, segregation of multiple independent mendelian loci. phenotype cant be easily predicted from genotype and vv

Question 4

What does polygenic theory assume?

Answer 4

that genes are additive.
created different additive classes different by one unit and that random environmental variation then created a bell curve.

Question 5

what is the number of phenotypic classes expected when there are n bi allelic additive genes with equal effect?

Answer 5

2n +1

Question 6

what are the components of phenotypic variation

Answer 6

Vp = VG+VE
VE = estimated if inidividuals of uniform genotypes (VG=0) are grown in different environmental conditions
VG = estimated if individuals of different genotypes grown in same envrionmental conditions VE=0

Question 7

what are the components of genotypic variaition

Answer 7

VG = VA + VD + VI
VA - additivie genetic variance (sum of phenotypic effects of alleles when assembled in genotypes
VD - deviation of genotypic values from their values under the additive gene action due to dominance
VI - deviation of genotypic values under additive gene action due to interaction among loci = epistatic or interaction genetic variance

Question 8

what are the components of envrionmental variation

Answer 8

VE = VEW + VEC(s) + VEC(t) + VEC(m)
proportion of total enviro variation caused by unknown or tangible causes plus spatial, temporal and maternal.
(common envrionmetn causing individuals to be more similar to each other than individuals reared in different common environments
spatial eg different vials
temporal - different feeding times
maternal - maternal nutrition differs between females

Question 9

what is genotype environment correlation and how can this be removed as a factor?

Answer 9

when exposure to environmental conditions depends on an organisms genotype.
remove as a factor by randomising vials and environments.
if dont control leads to increase in variation
or lumped in with VG increasing it by 2covGE
VP = VG + VE + 2CovGE

Question 10

What is VGE

Answer 10

component of phenotypic variation due to genotypic variation in respinse to different environments ie. phenotypic plasticity. (genotype producing different phenotypes in different environments)- estimated or lumped into GE

Question 11

what is the full equation for Vp

Answer 11

Vp = VA + VD + VI + 2COVG + VEW + VEC(S) + VEC(T) + VEC(M) + VGE

Question 12

what can be assumed if subcomponents of Vp are missing

Answer 12

that they are assumed to be zero or have been lumped into another category

Question 13

what does heritability range from?

Answer 13

0-1

Question 14

what is the equation for broad sense heritability

Answer 14

H2= VG/VP
Portion of total phenotypic variation attributable to genetic effects
(upper case H)

Question 15

what is narrow sense heritability

Answer 15

offten just heritability
h2 = VA/VP
portion of total phenotypic variation attributable to the sum of phenotypic effects of alleles when assembled in genotypes
main cause of resemblance between relatives.
lower case h

Question 16

how can variance of components be measured for heritability estimation?

Answer 16

by comparing different classes of relatives and knowing the fraction of genes they share (covariance) - parent offspring regression. and other relatives using ANOVA and twin studies

Question 17

what is h^2 equal to

Answer 17

=VA/VP = Cov(mp,o)/Var(mp)

no brackets

Question 18

how do you calculate the slope on a graph in parent offspring regression

Answer 18

covariance of parents and offspring / varaiance - h^2 = slope
slope approximates the heritability of the trait when offspring values are regressed against the average trait in parents

Question 19

what is the covariance of parents and offspring equal to

Answer 19

the sum of (mp value = mp mean) x (o value - o mean) /N

Question 20

what is the hertiability if only one parent value is used in parent offspring regression

Answer 20

twice the slope

Question 21

what are the concordance rates for CF, hypertension, type 1 diabetes, measles in mono and dizygotic twins

Answer 21

CF 100 25
hypertention 30 10
type 1 diabetes 35 6
measles 76 56

Question 22

what does it mean if MZ concordance rate is significantly higher than DZ concordance rates

Answer 22

there is genetic influence

Question 23

what type of trait is CF

Answer 23

monogenic trait - 100% concordance in MZ

Question 24

what does a significant difference but not 100% between mono and di twins concordance rate show?

Answer 24

complex polygenic trait- enviro acting.

Question 25

what is breeders equation?

Answer 25

R =h^2S
R = response to selection
S = selection differential (ie. strength of selection)

Question 26

how do you calculate heritability estimate in twin studies

Answer 26

2(rMz-rDz)