genetics- penetrance and expressivity

expressivity

degree to which a geno is phenotypically expressed

depends on genetics and environment

general description

constant expressivity

geno shows expected pheno

genetically identical and all look the same

=100

variable expressivity

geno shows a range of pheno

genetically identical and same genetic background but all look different b/c environment

>100

penetrance

expressed as the percent of a population that expresses a trait

pheno depends on both geno and environment

calculations and clincial research

complete penetrance

all organisms with same geno show the expected pehno

100%

all the same

incomplete penetrance

not all of the organisms show the expected pheno

<100%

some genes have both

incomplete penetrance and variable expresivity

^often used together

show expected pheno but also get a range

effects of environment

age of onset

different genes are expressed at different times during the life cycle and programmed activation and inactivation of genes influences many traits

ex: pattern baldness

sex affects the expressioin of some

autosomal genes-NOT SEX-LINKED

sex-limited traits

appear in one gender but not the other

AUTOSOMAL

sex-influenced traits

appear in BOTH genders but genders show either a difference in frequency of occurance or an altered relationship between geno and pheno

different expression between male and female

ex: pattern baldness

AUTOSOMAL

temp affects…

phenotypes, enzymes work best at certain temps