Question

Mapping genes with recombination frequencies in Drosopna 1. Suppose you know of three linked loci on the Drosophila X chromosome (a, b, and c). Assume that you are starting out with true-breeding stocks that show all three recessive traits and true-breeding stocks that show all three dominant traits. A. If you wanted to do a 3-point test cross to map the three loci, how would you set up the cross? What genotypes do you use for males and females in the testcross? B. How how you derive the genotypes that you are going to use for the testcross? C. What phenotype classes do you expect to see in your testcross progeny? (Don't worry, about progeny numbers; just give the progeny classes.) In Drosophila, fused vein (fu), sable body (s), and singled bristle (sn) are recessive alleles of three linked genes (wild type, dominant alleles being fu+, s+, and sn+). Note that these genes are listed in alphabetical order, not necessarily according to their relative positions. Trihybrid females were crossed to males showing the three dominant traits, and the progeny phenotypes were: Females: fu+s+ sn+ 1029 Males: 69 321 17 fut st snt fu s+ sn+ fut st sn fu+ s sn+ fu+ s sn fu s sn+ fu s+ sn fu s sn 99 307 21 91 75 A. Give the genotypes of the parental females and male. B. Construct a genetic map of the region.

Answer 1

1.) (A:) To do 3- bolot test cross to mab three loci we need to cross a heterozygous dominant female for all three loci with homozygou's recessive male for all three wei Genotype of male - aabber Genotype of female - Aa Bb Cve (B) Genoty be of female is found if- a cross between homozygous dominant female CAA BB CC) is cross with recessive male (aabbcc). Genotype of male is found between cross of recessive male and female nie, both maring genotope Caablite). (C) Phenoty be classex ABG, abc, Abe, GBC, ABC, ab C, Ab C , abc

(2) (A) Genotype of parental femalen futlfu st/s Smt/sm. Genotype of parental male- fulfu; s/s Solson B) According to the ofbsbring count in male sn is . i present in belween fufs j.e. gene order fu In S or senty Distance bwe Ju fn (321-4.3082) (17421) goy (3001) = 32.82% ox 32.82 CM Gabby Distance 6100 snt sa (99791) 4 (17421) mons 2024 = 18-24% on 19.24CM Gabbyo X,) Mob: la (NOT IN SCALO 32.820M 11:24CM - 44.06 ---