Question

Let’s suppose that a gene in fruit flies, which we will call gene B, follows a maternal effect pattern of inheritance. A loss-of-function allele (b) is recessive and lethal. Two phenotypically normal flies were crossed and all of the offspring died during early embryonic development. What are the possible genotypes of the dead offspring’s mother, father, maternal grandmother, maternal grandfather, paternal grandmother, and paternal grandfather? Note: In some cases, more than one genotype may be possible

offspring’s mother:

offspring’s father:

offspring’s maternal grandmother:

offspring’s maternal grandfather:

offspring’s paternal grandmother:

offspring’s paternal grandfather:

Answer 1

"b" allele is recessive and lethal. Two phenotypically normal flies were crossed and all of the offspring died. Which means that these two parents must be heterozygous for the B gene. So both of them can transmit the recessive lethal b allele to the offsprings.  

Genotype of the Mother: Bb

Genotype of the father: Bb

Both parents are heterozygous, so at least one of their parent must have the recessive allele . Either Both paternal and maternal grandparents were heterozygous or one of them heterozygous and one Homozygous.

Offspring's maternal grandmother's genotype : BB or Bb

Offspring's maternal grandfather's Genotype: Bb or BB

OffspriOf's paternal grandmother's genotype: BB or Bb

Offsprings paternal grandfather's genotype: Bb or BB