Extensions of Mendelian Inheritance Flashcards
Incomplete Penetrance
A dominant allele does not influence the outcome of a trait in a heterozygote individual
Expressivity
The degree to which a trait is expressed
If 60% of heterozygotes carrying a dominant allele exhibit a trait ____
the trait is 60% penetrant
Incomplete dominance
The heterozygote phenotype is intermediate between the homozygotes.
Over-dominance (Heterozygous advantage)
The heterozygote for sickle cell has an advantage over the homozygous dominant and recessive.
Type AB blood is an example of what?
Codominant
Sex-linked traits
Traits are governed by genes on the sex chromosomes. Alleles are dominant in one sex and recessive in the opposite
When are sex influenced visible?
Heterozygotes (Ss for males = scurs; Ss for females= no scurs)
Are sex-influenced traits autosomal?
yes
Sex-limited inheritance
Traits that only occurs in one of the sexes
Lethal alleles
One that has the potential to cause the death of an organism
Conditional lethal alleles
May kill an organism when certain environmental conditions prevail
Agouti gene in mice?
Homozygous for agouti yellow allele = dead mice
Dominant lethal
Huntingtons disease
Recessive lethal
cystic fibrosis, manx cats, agouti gene mice
Complementation
Same phenotype caused by mutations in different genes. Wild type offspring are produced from a cross between parents that both display the same recessive phenotype
Epistasis
A gene can mask the phenotypic effects of another gene. Both parents have recessive phenotype, offspring has WT phenotype
Gene modifier effect
Alleles of one gene modifies the phenotypic outcome of alleles of a different gene
Gene redundancy
Existence of multiple genes that perform the same function. Loss of one gene does not change phenotype, loss of two genes changes phenotype
