Genetics Questions, Please help! A diploid organism is usually purple due to the

Question

Genetics Questions, Please help!

A diploid organism is usually purple due to the following pigment synthesis pathway: A geneticist has isolated two mutant strains, one brown and one orange, each of which is homozygous for a recessive, loss-of-function mutation that inactivates one of the two enzymes in the pathway. When the brown (a/a: B/B) and orange (A/A: b/b) strains were mated, all F_1 progeny were (as expected) purple. These F_1's were then selfed to produce the next (F_2) generation, which showed phenotypic ratios indicative of recessive epistasis with independent assortment (i.e., 9: 3: 4). If an F_2 individual that is purple is chosen (at random) and mated with an individual F_2 that is orange, what is the probability that only purple progeny will be seen in the F_3 generation (assume each single-pair cross produces hundreds of progeny)? If a purple F_2 is mated with an orange F_2 (as above), what is the probability that ALL THREE phenotypes (purple, orange and brown) will be seen in the F_3 progeny?

Explanation / Answer

9) Brown (aa, BB) and orange (AA, bb) colored organisms are mated together

F1 progeny are all purple with genotype (Aa, Bb)

F2 produced by selfing F1

Purple crossed with orange

AABB X AAbb

All offsprings are purple

Therefore, if purple and orange offsprings from F2 generation are crossed,there ia 100% chance that F3 offsprings will be purple.

AB Ab aB ab AB AABB (purple) AABb (purple) AaBB (purple) AaBb (purple) Ab AABb (purple) AAbb (orange) AaBb (purple) Aabb (orange) aB AaBB (purple) AaBb (purple) aaBB (brown) aaBb (brown) ab AaBb (purple) Aabb (orange) aaBb (brown) aabb (brown)

Related Questions

Navigate

• Browse (All)
• Browse G
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.