Topic 3 Flashcards
Mutations of haplosuffient genes are _______
recessive
Dominant negative (lethal)
homozygous is mutant, sometimes is lethal. Heterozygous is mutant, but not lethal
ratio of dominant lethal alleles
2 domiant to 1 recessive
allelic series
dominace hierarchy of multiple alleles
null allele
non-functional and likely recessive to all other alleles
hypomorphic allele
has partial function
Incomplete dominance
appearance of 3 phenotype that blends 2 parental ones (no clear dominance)
Codominance
More than 1 allele is dominant, causing both parental phenotypes to be displayed
penetrance
the proportion of individuals of the same genotype that will either express the determined phenotype or not express it at all
What determines penetrance of the phenotype?
modifier genes
environmental factors
allelic variation
complex genetic and environmental interactions
expressivity
the degree or intensity with which a genotype is expressed (all display mutation, but there are many degrees of severity
pleiotropy
one gene controlling 2 or more apparently unconected phenotypes
polygenic inheritance
a phenotype affected by many different genes
________ _________are often polygenic and their effect on the phenotype incremental
Qualitative traits
How to test if a phenotype is due to expression of a single locus or more?
complementation tests show that if complement does not occur, it indicates alleslism. Complementation indicates non-allelic mutants
allelism
one locus involved
non-allelic mutants
more than 1 gene is responsible for same phenotype
Suppressor mutations
mutation that suppresses other mutations
Enhancer mutation
strengthens mutant phenotype
Intra-genic interaction (allelic)
dominance, recessiveness, co-dominance, incomplete dominance
Allele-environment interaction
penetrance, expressivity
Extra-genic interaction
suppresion, enhancement, genetic pathways
Additive gene action
alleles of 2 genes generating 4 phenotypes in a single trait (2 loci, 1 trait, 4 phenotypes). Has same phenotypic ratio 9:3:3:1
Complementary gene action
only 2 phenotypes. Homozygous recessive for both/either genes produces 1 phenotype, while homozygous dominant for both/either gene produces a different phenotype (9:7 ratio)
redundancy (duplicate gene action)
dominant alleles of both genes overpowers each others recessive alleles and produces the same phenotype (15: 1 ratio)s
Epistatic
a mutant allele of 1 geneoverrides the phenotypic effect of a mutant allele of another gene when both are present in the same genotype (ex: white eye is expressed over the red eye)
hypostatic
suppressed phenotype
Dominance vs. epistasis
Dominance - intra-allelic gene interaction (1allele hides the other allele of the same locus)
Epistasis - inter-allelic gene interaction (1 gene hides affect of another gene)
recessive epistatis
when the recessive allele of 1 gene masks the effect of either (dom/rec) allele of the second gene (9:3:4)
dominant epistasis
when the dominant allele of 1 gene masks the effects of either (dom/rec) allele of the second gene (12:3:1)
