A new gene is being investigated in fruit flies. The recessive allele of this gene (b) causes the wings to develop a blue color, while the dominant allele (b+) permits wild-type colorless wings to develop. Preliminary studies indicate that this new gene is located on the X-chromosome. You decided to perform a two-point testcross to determine its position relative to the well-established garnet eyes gene (g). You cross a female heterozygous for both genes with a testcross male fly and obtain the male offspring results shown in table 1, below. Is the original female a coupling or repulsion heterozygote? What is the map distance between genes b and g?. Based on these results, gene b must be located between what two genes on the map? You perform another two-point testcross between gene b and gene v and obtained the results in table 2, below. Now, you can localize gene b to be specifically between which two genes?

Biology: The Unity and Diversity of Life (MindTap Course List)
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Author:Cecie Starr, Ralph Taggart, Christine Evers, Lisa Starr
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Chapter23: Fungi
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A new gene is being investigated in fruit flies. The recessive allele of this gene (b) causes the wings to develop a blue color, while the dominant allele (b+) permits wild-type colorless wings to develop. Preliminary studies indicate that this new gene is located on the X-chromosome. You decided to perform a two-point testcross to determine its position
relative to the well-established garnet eyes gene (g). You cross a female heterozygous for both genes with a testcross male fly and obtain the male offspring results shown in table 1, below. Is the original female a coupling or repulsion heterozygote? What is the map distance between genes b and g?. Based on these results, gene b must be located between what two genes on the map? You perform another two-point testcross between gene b and gene v and obtained the results in table 2, below. Now, you can localize gene b to be specifically between which two genes?

Table 1: phenotype
wild-type
garnet eyes
blue wings
garnet eyes & blue wings
# male offspring
Table 2: phenotype
wild-type
vermillion eyes
blue wings
vermillion eyes & blue wings
# male offspring
472
79
27
427
23
413
478
81
Transcribed Image Text:Table 1: phenotype wild-type garnet eyes blue wings garnet eyes & blue wings # male offspring Table 2: phenotype wild-type vermillion eyes blue wings vermillion eyes & blue wings # male offspring 472 79 27 427 23 413 478 81
SC
ec
CV
ct
9.1
10.5
9.2
15.9
11.2
10.9
66.8
Drosophila X chromosome
scute bristles
echinus eyes
crossveinless wing s
cut wings
vermilion eyes
garnet eyes
forked bristles
Transcribed Image Text:SC ec CV ct 9.1 10.5 9.2 15.9 11.2 10.9 66.8 Drosophila X chromosome scute bristles echinus eyes crossveinless wing s cut wings vermilion eyes garnet eyes forked bristles
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