Lecture 5: Mendelian inheritance variations & phenotypic plasticity

Codominance

when heterozygotes express both alleles

test cross

genetic cross between an unknown genotype and a homozygous recessive individual

XX/XY system

mammals and some insects, sperm determines sex, female: XX male: XY

ZZ/ZY system

birds, butterflies, some reptiles, egg determines sex, female: ZW male: ZZ

sex-linked trait for XX/XY system

x-linked

sex-linked trait for ZZ/ZY system

z-linked

complete dominance

One allele completely masks the other in a heterozygote

incomplete dominance

Neither allele is completely dominant

co-dominance

Both alleles are fully and equally expressed in the heterozygote

G x E interactions

describe how genetic predispositions (genes) and environmental factors (like diet, stress, pollutants) influence traits and health outcomes differently

phenotypic plasticity

one genotype can produce different phenotypes in different environments

difference between phenotypic plasticity and traits that have a genetic basis

Same genotype → different phenotypes across environments, traits change when environment changes

difference between phenotypic plasticity and traits that have a genetic basis

Different genotypes → different phenotypes, even in the same environment, trait unchanged across environments