biol 1040 - lecture 8

inheritance and heritability

what is the difference between genotype and phenotype?

genotype is an individual’s genetic makeup, while a phenotype is the observable characteristics/traits one has

what is a continuous/quantitative trait?

a trait where phenotypes are not separated into a few distinct categories - there is a RANGE of values (e.g., height)

why do many loci produce continuous variation?

as the number of genes involved increases, the number of possible genotypes and phenotype combinations increases, producing a continuous range of phenotypes

what can phenotypic variation be influenced by?

nature (genetic effects) and nurture (environmental effects)

what is heritability?

the proportion of observed phenotypic variation among individuals in that population that contributes to genetic variation

how do we measure heritability?

if genetics contributes to a trait, people who are more genetically related should tend to be more phenotypically similar

example: siblings are more genetically related than cousins

what is MZ twins?

monozygotic twins, often called identical twins — much more genetically similar than DZ twins

what is DZ twins?

dizygotic twins, often called fraternal twins

what does a large difference between MZ and DZ twin similarity suggest?

it suggests a stronger genetic contribution to variation in that trait, resulting in a higher heritability estimate

parent-offspring regression

is heritability the same as genetic determinism?

no

heritability depends on the __

environment

controlled environment:

low environmental variation → genetics can account for a larger proportion of observed variation

variable environment:

high environmental variation → genetics can account for a smaller proportion of observed variation

heritability is not a __ of a trait

fixed property

explain what the gene x environment interaction is

when the same genotype may produce different phenotypes depending on the environment