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. You testcross the F1 dihybrids with the double-mutant line (the “tester” genotype) and obtain four phenotypes in the F2: wild type apricot, blunt apricot blunt Determine the following for each F2 phenotype: the haploid genotype of the gamete it received from the F1 dihybrid its full diploid genotype whether the gamete it received from the F1 dihybrid was recombinant (REC) or nonrecombinant (nonREC). Complete the table by dragging the white labels to the gray targets, the blue labels to the blue targets, and the pink labels to the pink targets. Labels can be used once, more than once, or not at all. View Available Hint(s) ResetHelp ABGroup 1 AB AabbGroup 2 Aabb AbGroup 1 Ab aaBbGroup 2 aaBb aBGroup 1 aB aabbGroup 2 aabb abGroup 1 ab RECGroup 3 REC AaBbGroup 2 AaBb non RECGroup 3 non REC G1 G1 G1 G1 G2 G2 G2 G2 G3 G3

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

A pure-breeding double-mutant (apricot, blunt) has aabb genotype, wild-type wasp has genotype AABB. If we cross them:

P: aabb x AABB

F1: all the genotypes would be AaBb

If we ten cross the F1 dihybrids with the double-mutant line:

AaBb x aabb

F2: (table)

The four phenotypes are: 1) wild-type, 2) wild type apricot-short, 3) pale orange-wild type blunt, 4) double-mutant.

The possible haploid genotypes of the gamete it received from the F1 dihybrid: AB, Ab, aB, ab. AB and ab are nonrecombinant (nonREC), like those from parents, while Ab and aB gamets are recombinant (REC) .