module 14 Flashcards
complex traits
characteristics that are determined by several genes and are significantly influenced by environmental factors
meristic traits
can be expressed in whole numbers
threshold traits
traits that are inherited due to the contributions of many genes
frequency distribution
trait is divided arbitrarily into a number of discrete phyenotypic categories
normal distribution
traits of interest varies ina symmetrical way around an average value
covariance
the degree of variation between two variables within a group
correlation coefficient (r)
the strength of associations between two variables
polygenic
influenced by two or more genes
polygenic inheritance
the transmission of traits that are governed by two or more genes
quantitative trait locus (QTL)
the location on a chromosome that harbors one or more genes that affect the outcome of a quantitative trait
Vg
Genetic variance
Ve
environmental variance
Vp = Vg + Ve
- genetic and environmental factors are the only two components that determine a trait
- these factors are independent of one another
if Vg is high and Ve is low then
genetics is more important in promoting phenotypic variation in a population
if Ve is high and Vg is low then
the environment causes much of the phenotypic variation in a population
genotype-environmental interaction
genetics and environment interact to affect a trait
genotype-environment association
when certain genotypes are preferentially found in a particular environment
heritability
the amount of phenotypic variation within a group of individuals that is due to genetic variation
when heritability = 1
all the phenotypic variation in a group is due to genetic variation
when heritability = 0
all the phenotypic variation is due to environmental factors
hb^2
= Vg/Vp
Vg (equation)
= Va(additive) + Vd(dominant/recessive) + Vi(interact)
narrow sense heritability
the heritability of a trait due to the additive effects of alleles
hn^2 =
Va/Vp and robs/rexp
realized heritability
the response to selection, hn^2 = R/S, mean of the offspring divided by the mean of the starting population (parents)
heterosis
when two different inbred strains are crossed to each other, the offspring are more vigorous than either parent
the dominance hypothesis
the effects of the dominant alleles explain the favorable outcome in a heterozygote
the overdominance hypothesis
the resulting hybrids are more vigorous because they are heterozygotes for one or more genes that display overdominance
