DNA problem 4. In Drosophila, echinus eye color (e) is recessive to wildtype eye
ID: 34825 • Letter: D
Question
DNA problem
4. In Drosophila, echinus eye color (e) is recessive to wildtype eyes (ef), crossveinless wings (c) is recessive to wildtype wings (c^+), and scute bristles (s) is recessive to wildtype bristles (st). Two pure pure-breeding strains of flies are crossed to generate Fi offspring that are heterozygous for all three genes. The Fi flies are then crossed with flies that are homozygous for the recessive alleles in a three-point testcross. The progeny of the testcross are: Phenotype of testcross progeny Parental, SCOI, Number Genotype (for your own benefit) sco ii,or DCO? Echinus eyes, wildtype wings, wildtype bristles 8576 wildtype eyes, wildtype wings, scute bristles 977 wildtype eyes, crossveinless wings, wildtype bristles 716 Echinus eyes, wildtype wings, scute bristles 681 wildtype eyes, crossveinless wings, scute bristles 8808 Echinus eyes, crossveinless wings, scute bristles 4 Echinus eyes, crossveinless wings, wildtype bristles 1002 wildtype eyes, wildtype wings, wildtype bristles 1 Total offspring 20764 I a) In the spaces provided above classify each group of progeny as Parental (=non recombinant), SCO I, SCO II, or DCO (0.5 pt. total).Explanation / Answer
Phenotype of testcross
Number
Genotype
Parental, SCOI, SCO II, or DCO ?
Echinus eye,
wildtype wings,
wildtype bristles
8576
ee cc+ ss+
Parental
wildtype eye,
wildtype wings,
scute bristles
977
ee+ cc+ ss
Sco II
wildtype eye,
crossveinless wings,
wildtype bristles
716
ee+ cc ss+
SCO I
Echinus eye,
wildtype wings,
scute bristles
681
ee cc+ ss
SCO I
wildtype eye,
crossveinless wings,
scute bristles
8808
ee+ cc ss
Parental
Echinus eye,
crossveinless wings,
scute bristles
4
ee cc ss
DCO
Echinus eye,
crossveinless wings,
wildtype bristles
1002
ee cc ss+
Sco II
wildtype eye,
wildtype wings,
wildtype bristles
1
Ee+ cc+ ss+
DCO
TOTAL
20764
Phenotype of testcross
Number
Genotype
Parental, SCOI, SCO II, or DCO ?
Echinus eye,
wildtype wings,
wildtype bristles
8576
ee cc+ ss+
Parental
wildtype eye,
wildtype wings,
scute bristles
977
ee+ cc+ ss
Sco II
wildtype eye,
crossveinless wings,
wildtype bristles
716
ee+ cc ss+
SCO I
Echinus eye,
wildtype wings,
scute bristles
681
ee cc+ ss
SCO I
wildtype eye,
crossveinless wings,
scute bristles
8808
ee+ cc ss
Parental
Echinus eye,
crossveinless wings,
scute bristles
4
ee cc ss
DCO
Echinus eye,
crossveinless wings,
wildtype bristles
1002
ee cc ss+
Sco II
wildtype eye,
wildtype wings,
wildtype bristles
1
Ee+ cc+ ss+
DCO
TOTAL
20764
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