QUESTION 1 Are the genes for white eyes and black body linke

QUESTION:

1) Are the genes for white eyes and black body linked?

2) Are the genes for star eyes and black body linked?

3. During crossing over, when homologous chromosomes randomly exchange genes, which of the following pairs of genes are MOST likely to travel together?

a) yellow body & bar eyes

b) curved wings & star eyes

c) sepia eyes & ebony body

d) spineless bristles & sepia eyes

Part 1: Gene linkage groups Below are some of the genes mapped out to the four chromosomes (or linkage groups). Answer the following questions using this diagram. Chromosome 3 Chromosome 1 (X) Chromosome 2 Chromosome 4 Bent wing Yellow body cubitus veins Net veins 0.0 E Scute bristles 0.0 Aristaless antenna 0.0 zsTR:- Roughoid eyes 0.0 Shaven hairs less scutellum 1.5 White eyes 1.3 Star eyes 0.2 Veinlet veins Groove 3,0 Facet eyes Held-out wings Eyeless Echinus eyes 5.5 7.5 Ruby eyes 13.0 Dumpy wings Clot eyes 13.7 Crossveinless wings 16.5 20.0 Cut wings Javelin bristles 19.2 singed bristles 21.0 26.0 Sepia eyes 27.7 Lozenge eyes Hairy body 26.5 33.0 Vermilion eyes 36.1 Miniature wings 41.00 Dichaete bristles 43.2 I Thread arista Sable body 43.0 Black body 44.0 Garnet eyes 48.5 44.0 Scarlet eyes 51.0 Reduced bristles 48.0 Pink eyes Forked bristles 56,7 54.5 Purple eyes 50.0 Curled wings 54.8 Short bristles 57.0 Bar eyes 58.2 Stubble bristles Fused veins Light eyes 58.5 Spineless bristles 59.5 55.0 62.5 Carnation eyes 57.5 Cinnabar eyes 58.7 Bithorax body 66.0 Bobbed hairs 66.7 Scabrous eyes 62.00 Striped body vestigial wings 63.00 Glass body 67.0 Delta veins 72.0 Lobe eyes Hairless bristles 69.5 Ebony body 75.5 Curved wings 70.7 74.7 Cardinal eyes 91.1 Rough eyes Plexus wings 100.5 100 Claret eyes 104.5 Brown eyes r Minute bristles 107.00 Speck body 106-2 Figure 7.15 Genetics AConceptualApproach, Sixth Edition

Solution

1. The gene for white eye is on chromosome 1, and that of black body is on chromosome 2. They cannot be linked.

2. The genes for star eyes and black body are both on the same chromosome (#2) and the distance between them is 48.5 - 1.3 = 47.2 cM (< 50 cM). Hence, they are linked.

3. Distances between the given genes:

a) yellow body & bar eyes: 57 - 0 = 57 cM

b) curved wings & star eyes: 75.5 - 1.3 = 74.2 cM

c) sepia eyes & ebony body: 70.7 - 26 = 44.7 cM

d) spineless bristles & sepia eyes: 58.5 - 26 = 32.5 cM Hence, these two genes are most likely to travel together because of least distance (greatest linkage) between them