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sjohn092 sjohn092
wrote...
Posts: 27
10 years ago
Recombination in dihybrid crosses
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.

http://007742736x.reader.chegg.com/homework-help/questions-and-answers/recombination-dihybrid-crossesyou-screened-new-recessive-mutations-species-waspwasps-homoz-q4289166

the link above is the diagram (along with the same question I asked)


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padrepadre
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10 years ago
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sjohn092 Author
wrote...
10 years ago
the attachment is the same, but this is for a dihybrid cross, not a trihybrid.
wrote...
Staff Member
Educator
10 years ago
the attachment is the same, but this is for a dihybrid cross, not a trihybrid.

Did you end up with the answer? Could you please update us?
nanduanandu,  stude3,  Jules12345
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sjohn092 Author
wrote...
10 years ago
yes, i did end up with an answer.
wrote...
Staff Member
Educator
10 years ago
Post it lol

I was going crazy figuring this out
Mastering in Nutritional Biology
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sjohn092 Author
wrote...
10 years ago
I can't seem to show the diagram with my answers.

But here's the answer in words.

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 F2 phenotypes. Therefore, such testcrosses allow you to determine the haploid genotype of the gametes produced by the F1 dihybrid.
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wrote...
Staff Member
Educator
10 years ago
Thanks a lot man, appreciate it
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sjohn092 Author
wrote...
10 years ago
no worries. I'm sorry for getting you all worked up on this question.

wrote...
10 years ago
Thank you so much  Grinning Face
wrote...
9 years ago
thank you!
wrote...
9 years ago
This question is confused, like the majority on the mastering genetics site. You have to infer that the gametes that are directly received from the trihybrid cross are given proportionately in the way the are listed moving from most common to least common, and assign relative values before you can begin to decide which are recombined and which are not recombined.
chandanasairam
wrote...
9 years ago
Need to distinguish between
the different bacteria; we are interested in the exconjugants.
Antibiotic resistance
and auxotrophy markers
wrote...
9 years ago
thank you
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