A- Thomas Hunt Morgan and Linkage in Drosophila Before we get started, a note on

Question

A- Thomas Hunt Morgan and Linkage in Drosophila Before we get started, a note on fruit fly genetic notation: Wild type-the most common phenotype in nature (wild type is not always dominant, though) Wild type alleles are designated with (t) A recessive, non wild type allele is abbreviated with lower case letters-e.g. pr purple eyes A dominant, non wild type allele is given a capital let Ap aristapedia Morgan A puzzling cross the first explanation of linkage vestigial wings did a cross involving a mutant eyed, He then did a test cross with the dihybrids: What would you expect given what we know about independent assortment? Morgan's results: (note the numbers and be impressed!) Genetics

Explanation / Answer

Eye color: pr+ = red or pr = purple

Wing morphology: vg+ = normal wings or vg = vestigial wings

pr+ pr+ vg+vg+   x   pr pr vg vg

F1 offspring-------------- pr+ pr vg+ vg

F2: offsprings

phenotype

Expected ratios

Red eyed normal wings (pr+_ vg+_)

9

Purple eyed normal wings (pr_ vg+_)

3

Red eyed vestigial wings (pr+_ vg_)

3

Purple eyed vestigial wings (pr_ vg_)

1

==================================================

Test cross

F1 female pr+ pr vg+ vg with pr pr vg vg male.

gametes

pr vg

pr+ vg+

pr+ pr vg+ vg

pr vg+

pr pr vg+ vg

pr+ vg

pr+ pr vg vg

pr vg

pr pr vg vg

Progeny were:

phenotype and genotype

ratio

Red eyed normal wings (pr+pr vg+vg)

1/4

Purple eyed normal wings (prpr vg+vg)

1/4

Red eyed vestigial wings (pr+pr vgvg)

1/4

1/4

1/4

phenotype

Expected ratios

Red eyed normal wings (pr+_ vg+_)

9

Purple eyed normal wings (pr_ vg+_)

3

Red eyed vestigial wings (pr+_ vg_)

3

Purple eyed vestigial wings (pr_ vg_)

1

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