3. (1 pt) In Martian genetics, blue skin is dominant to yellow, and green eyes is dominant to red.
You cross: A Martian with the dominant phenotype for skin and eyes (blue skin, green eyes)
with a yellow-skinned, red-eyed Martian. The progeny are:
73 blue skin, red eyes
75 yellow skin, green eyes
7 blue skin, green eyes
6 yellow skin, red eyes
Estimate the map distance between the loci for skin color and eye color. Show your work.
State the phenotypes of the two parents of the original Martian with dominant skin and eye color
traits.
5. (2 pts) List each of the 5 major assumptions of the Hardy-Weinberg Principle. In one short
sentence, explain the genetic consequence of breaking each of these assumptions.
6. A line of drosophila has been constructed with three recessive mutations, all on the same
chromosome:
SC = presence of thorax bristles; sc = loss of thorax bristles (“scute”)
EC = smooth eye surface; ec = roughened eye surface (“echinus”)
VG = wild-type or normal wings; vg = vestigial wings
Now cross homozygous dominants with homozygous recessives:
Parental generation: SCECVG/SCECVG × scecvg/scecvg
F1 generation: SCECVG/scecvg
Now cross F1 homozygous recessives:
SCECVG/scecvg × scecvg/scecvg
F2 generation: This cross produces an F2 generation with 6 different phenotypes:
SC EC VG 510 (Parental combination of alleles)
sc ec vg 497 (Parental combination of alleles)
sc EC VG 23 (recombinant combination of alleles)
SC ec vg 27 (recombinant combination of alleles)
sc ec VG 48 (recombinant combination of alleles)
SC EC vg 42 (recombinant combination of alleles)
sc EC vg 5 (recombinant combination of alleles)
SC ec VG 4 (recombinant combination of alleles)
Total flies in F2 3 1156
Assignment:
a) (1 pt) From these genetic data, and using the mapping example provided, determine the
recombination frequencies between each pair of genes (there are 3 pairs: sc/ec; ec/vg; sc/vg ).
b) (1 pt) After you have calculated the recombination frequencies for each gene pair, construct a
genetic map (again, using the mapping example provided).
c) (1 pt) Two recombinants are much rarer than the other types. Why? (1-2 sentences should be
sufficient)
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