Exam 4- Allelic interactions & epistasis Flashcards
In ___ the heterozygous phenotype is intermediate between the two homozygous phenotypes
incomplete (or partial) dominance
F1 hybrids do not look like either parent:
they display an intermediate phenotype
a quantitative phenotype determined by gene dosage
molecular basis for incomplete dominance
R1 = wild type; promotes
___ pigment production
red
R2 = _______; no pigment produced
loss of function
the snapdragon R gene is ___
haploinsufficient
variable penetrance/ expressivity:
___ genotypes
___ phenotypes
same genotypes; different phenotypes
incomplete dominance:
___ genotypes
___ phenotypes
different genotypes; different phenotypes
in ___ the phenotypes of both alleles are visible in the heterozygote
co-dominance
the ____ ___ encodes an enzyme (glycosyl transferase) that adds terminal sugar molecules to H substance, which is expressed on the surface of RBCs
I gene
the ___ __ encodes a version of the enzyme that adds N-acetylglucoseamine (“A sugar”) to the H substance, creating the A antigen
IA allele
the ___ ___ encodes a version of the enzyme that adds galactose (B sugar) to the H substance, creating the B antigen
IB allele
the __ ___ is a null allele ( complete loss of function) and cannot promote the addition of either sugar to H substance
i allele
AY is dominant over A for ___ ___; but AY is recessive to A for ____
coat color; lethality
an interaction between two alleles of the same gene, where the phenotype of one allele (the dominant allele) masks the phenotype of another allele (the recessive allele).
Dominance
an interaction between two different genes, where the phenotype of one gene (the epistatic gene) masks or modifies the phenotype of another gene (the hypostatic gene).
Epistasis
the recessive phenotype of the epistatic gene prevents the phenotypic expression of the hypostatic gene.
In recessive epistasis
recessive epistasis produces a characteristic ____ dihybrid ratio, if both genes exhibit complete dominance
9:3:4
dihybrid cross with co-dominance plus epistasis ratio
IAIB Hh x IAIB Hh
3:6:3:4
a method to determine whether two different mutations affect the same gene or two different genes
- both mutant phenotypes must be recessive
complementation test
