Wildtype Drosophila have red eyes Several different genes ar

Wild-type Drosophila have red eyes, Several different genes are known to affect The following eye mutants were crossed eye color in P1 Brown-eyed female X Scarlet-eyed male F1 All Wild-type red eyed flies F1 X F1 cross was made and the following results were obtained F2 146 brown-eyed flies 151 scarlet-eyed flies 50 white-eyed flies 444 wild-type red-eyed flies A. Explain this pattern of inheritance. (Give the genotypes of flies)

Solution

Answer:

Non epistatic Inter allelic genetic interaction:

In some cases two pairs of genes determine same phenotype but assorted independently, produce new phenotypes by mutual epistatic interaction. The F₂ ratio remains the same as 9:3:3:1.

Example:

Each gene pair affecting the same character complete dominance at both gene pairs, new phenotypes resulting from interaction between dominants, and also from interaction between both homozygous recessives.

Red-eye= A_B_

Brown-eye= A_bb

Scarlet-eye=aaB_

White-eye= aabb

AAbb (brown) x (Scarlet-eye)aaBB--------Parents

Ab                                 aB---------------------Gametes

              AaBb (red)----------------------------F1

AaBb x AaBb

AB

Ab

aB

ab

AB

AABB(red)

AABb(red)

AaBB(red)

AaBb(red)

Ab

AABb(red)

AAbb(brown)

AaBb(red)

Aabb(brown)

aB

AaBB(red)

AaBb(red)

aaBB(scarlet)

aaBb(scarlet)

ab

AaBb(red)

Aabb(brown)

aaBb(scarlet)

aabb(white)

Red : brown : scarlet : white = 9 : 3 : 3 : 1

444 : 146 : 151 : 50 = 9 : 3 : 3 : 1

	AB	Ab	aB	ab
AB	AABB(red)	AABb(red)	AaBB(red)	AaBb(red)
Ab	AABb(red)	AAbb(brown)	AaBb(red)	Aabb(brown)
aB	AaBB(red)	AaBb(red)	aaBB(scarlet)	aaBb(scarlet)
ab	AaBb(red)	Aabb(brown)	aaBb(scarlet)	aabb(white)