Question

You have screened for several new recessive mutations in a species of wasp. Wasps homozygous for apricot (aa) have pale orange eyes. (Wild-type eyes are brown.) Wasps homozygous for blunt (bb) have short wings. (Wild-type wings are long.) You make a pure-breeding double-mutant (apricot, blunt) line and cross it with wild-type wasps. The F1 is wild-type in appearance.

Answer 1

Wild Type:

• gamete from dihybrid = AB
• gamete from tester = ab
• full genotype = AaBb
• REC or nonREC? = nonREC (non recombinant)

Apricot, Blunt:

• gamete from dihybrid = ab
• gamete from tester = ab
• full genotype = aabb
• REC or nonREC? = nonREC (non recombinant)

Apricot:

• gamete from dihybrid = aB
• gamete from tester = ab
• full genotype = aaBb
• REC or nonREC? = REC (recombinant)

Blunt:

• gamete from dihybrid = Ab
• gamete from tester = ab
• full genotype = Aabb
• REC or nonREC? = REC (recombinant)

Step-by-step explanation:

"Recombination occurs when combinations of alleles not found in either parent are placed into gametes during meiosis in the F1 generation. The F1 can be thought of as having been formed from two haploid “input” gametes.

In this case, the F1 is a dihybrid with AB on one chromosome and ab on the other chromosome. You can tell this by looking at the parents. The F1 hybrid got AB from one parent and ab from the other parent (AB/ab). A dihybrid that is AB/ab can produce four possible “output” gametes through meiosis. Output gametes that match one of the input gametes are nonrecombinant (AB or ab). Output gametes with new combinations of alleles are recombinant (Ab or aB).

Its important to realize that its also possible to have a dihybrid who is Ab/aB instead. In this case, one parent was AAbb and the other parent aaBB. A dihybrid who is Ab/aB can also produce four possible "output" gametes through meiosis, but in this case the nonrecombinant gametes are Ab or aB and the recombinant gametes are AB or ab. In Part C, be sure to check the parents of the F1 trihybrid to determine their configuration of alleles before answering the question. Which gametes are nonrecombinant versus recombinant depends how the alleles are organized in the F1 trihybrid.

In a testcross with a homozygous recessive line (tester), the tester will contribute only recessive alleles that do not affect the phenotypes of the testcross progeny. Therefore, such testcrosses allow you to determine the haploid genotype of the gametes produced by the F1 dihybrid." - Mastering Genetics Pearson

**I have inserted an image below for further clarification - all rights reserved to Mastering Genetics Pearson**

Answer 2

The F1 will have mostly dominant phenotype, nevertheless, some recesive phenotype appears as aa - ab and bb

Step-by-step explanation:

If you make a pure-breeding double-mutant (apricot, blunt) line - you will have heterozygous ab

and if you cross it with wild-type wasps - you will have for apricot: AA - Aa and for blunt BB - Bb (as A and B are dominant gen)

Then, you could have for F1 breed:

*- ab / AA: Aa - BA

*- ab / Aa: aA - aa - bA - ba

*- ab / BB: Ba - aB

*- ab / Bb: aB - ab - bB - bb