Exam 4- Allelic interactions & epistasis

Question 1

In ___ the heterozygous phenotype is intermediate between the two homozygous phenotypes

Answer 1

incomplete (or partial) dominance

Question 2

F1 hybrids do not look like either parent:

Answer 2

they display an intermediate phenotype

Question 3

a quantitative phenotype determined by gene dosage

Answer 3

molecular basis for incomplete dominance

Question 4

R1 = wild type; promotes
___ pigment production

Answer 4

red

Question 5

R2 = _______; no pigment produced

Answer 5

loss of function

Question 6

the snapdragon R gene is ___

Answer 6

haploinsufficient

Question 7

variable penetrance/ expressivity:

___ genotypes
___ phenotypes

Answer 7

same genotypes; different phenotypes

Question 8

incomplete dominance:

___ genotypes
___ phenotypes

Answer 8

different genotypes; different phenotypes

Question 9

in ___ the phenotypes of both alleles are visible in the heterozygote

Answer 9

co-dominance

Question 10

the ____ ___ encodes an enzyme (glycosyl transferase) that adds terminal sugar molecules to H substance, which is expressed on the surface of RBCs

Answer 10

I gene

Question 11

the ___ __ encodes a version of the enzyme that adds N-acetylglucoseamine (“A sugar”) to the H substance, creating the A antigen

Answer 11

IA allele

Question 12

the ___ ___ encodes a version of the enzyme that adds galactose (B sugar) to the H substance, creating the B antigen

Answer 12

IB allele

Question 13

the __ ___ is a null allele ( complete loss of function) and cannot promote the addition of either sugar to H substance

Answer 13

i allele

Question 14

AY is dominant over A for ___ ___; but AY is recessive to A for ____

Answer 14

coat color; lethality

Question 15

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).

Answer 15

Dominance

Question 16

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).

Answer 16

Epistasis

Question 17

the recessive phenotype of the epistatic gene prevents the phenotypic expression of the hypostatic gene.

Answer 17

In recessive epistasis

Question 18

recessive epistasis produces a characteristic ____ dihybrid ratio, if both genes exhibit complete dominance

Answer 18

9:3:4

Question 19

dihybrid cross with co-dominance plus epistasis ratio
IAIB Hh x IAIB Hh

Answer 19

3:6:3:4

Question 20

a method to determine whether two different mutations affect the same gene or two different genes
- both mutant phenotypes must be recessive

Answer 20

complementation test