wild-type allele
the allele that is the most common, can be recessive or dominant (usually dominant)
mutant allele
mutation in the allele that leads to a different protein or no protein produced
gain-of-function mutations
arise due to excess protein (hypermorphic) or novel function (neomorphic mutations)
loss-of-function allele
produces less protein or a protein with diminished function
incomplete/partial dominance
heterozygous individuals have a phenotype that is intermediate to each homozygous phenotype
codominance
both alleles in a heterozygous individual are fully and equally expressed
lethal alleles
inviable with homozygous, and will alter the phenotypic ratio of crosses
sex-limited traits
both sexes carry the genes, but only one sex expresses the phenotype
sex-influenced traits
both sexes carry the genes, but the phenotype varies between the sexes
incomplete penetrance
traits that are nonpenetrant in some individuals but penetrant in other individuals
variable expressivity
a specific gene mutation leads to a range of differnent signs and symptoms in individuals who carry the same mutation
environmental effects
environmental factors can significantly influence phenotypes, even when a strong genetic basis exists
pleiotropy
when a single gene or genetic variabt influences multiple seemingly unrelated phenotypic traits.
this occurs because a gene’s product can be used in various cells and biological pathways, affecting different targets
phenotypic ratio for dihybrid cross: no interaction
9:3:3:1
yellow+smooth : yellow+wrinkly : green+smooth : green+wrinkly
pea pod colour and shape
phenotypic ratio for dihybrid cross: recessive epistasis
9:3:4
black : brown : yellow
labrador retriever coat colour
phenotypic ratio for dihybrid cross: dominant epistasis
12:3:1
white : yellow : green
summer squash colour
phenotypic ratio for dihybrid cross: complementary gene interaction
9:7
pink : white
sweet pea flower colour
phenotypic ratio for dihybrid cross: dominant supression
13:3
white : blue
blue pimpernel flower colour
