Question

Help with both please!

10. In a wild-type diploid fungus, protein E (encoded by the haplosufficient gene “E”') normally homodimerizes, and the E-E dimer catalyzes a biochemical reaction necessary for the production of a dark pigment. E represents a mutant, dominant negative allele of gene E. What is the predicted phenotype of a fungus cell of genotype ET/E”, and why? A) mutant (no pigment production), as E is haplosufficient B) mutant (no pigment production), as no E-E dimers will form in the heterozygous C) mutant (no pigment production), as the mutant allele EP is dominant D) wild type (normal production of the dark pigment), as E' is a negative allele E) wild type (normal production of the dark pigment), as E is haplosufficient 11. A mutant plant was found that has white flowers (wild type flowers are black). A pure- breeding plant with white flowers was bred to a pure-breeding plant with black flowers and the Fı plants all had gray flowers. What is the relationship between the black allele and the white allele of the flower color gene in these plants? A) White is dominant to black B) Black is dominant to white C) Black and white are codominant D) Black and white are incompletely dominant E) Black is haplosufficient whereas white is haploinsufficient

Answer 1

10) dominant-negative alleles produce the E^D enzyme which can inhibit the function of the E enzyme, E-E^D dimer is not functional, E^D-E^D dimer is also not functional.

E allele is haplosufficient, means in the presence of E allele and a null allele which does not code for the functional enzyme, one E allele can produce wildtype phenotype.

but the presence of dominant-negative allele reduces the amount of functional dimer of the enzyme, E dimerizes with E^D also so the phenotype is mutant because 50% of the E-E dimer compared to the wildtype cannot be produced in the heterozygotes with one dominant-negative allele and one normal allele.

so the answer is C) mutant ( no pigment production), as the mutant allele E^D is dominant.

11) the F1 progeny of black and white parents are gray that is progeny shows intermediate phenotype compared to both parents, this is an example of incomplete dominant.

if one allele was dominant the F1 would have shown that dominant phenotype.

D) black and white are incompletely dominant.