Problem Practice Worksheet 3 1. Consider the problem of comb shape inheritance in chickens, where walnut, rose pea, and single are observed as distinct phenotypes. How is comb shape inherited and what are the genotypes of the P1 generation of each cross? Use the following data to answer these questions. Cross 1. Single X single = all single Cross 2 walnut X walnut = all walnut Cross 3 rose X pea = all walnut Cross 4 F1 X f1 of cross 3 Walnut x walnut = 93 walnut 28 rose 32 pea 10 single
Two genes involved. W walnut w nonwalnut S nonsingle s single
Cross 1: Cross 2: Cross 3: Cross 4:
wwss X wwss = all ss (single) W_S_ X W_S_ wwSS X WWss = all walnut WwSs X WwSs
W_S_ (Walnut) 93 wwS_ (rose) 28 W_ss (pea) 32 Wwss (single) 10
Practice Problem Worksheet 3
2. In radishes, flower color may be red, purple, or white. The edible portion of the radish may be long or oval. When only flower color is studied, red X white yields all purple. If these F1 purples are interbred, no codominance is evident, and the F2 generation consists of 1.4 red:1/2 purple:1/4 white. Regarding radish shape, long is dominant to oval in a normal Mendelian fashion. A. the Determine F1 and F2 phenotypes from a cross between a true-breeding red long radish and one that is white oval. Be sure to define all gene symbols initially. R red, r white L long, l-oval P RRLL X rrll F1 RrLl (purple long) F2 Red long x = 3/16 Red oval x = 1/16 Purple long 2/4 x = 6/16 Purple oval 2/4 x = 2/16 White long x = 3/16 White oval x = 1/16
B. A red oval plant was crossed with a plant of unknown genotype and phenotype, yielding the data shown below. Determine the genotype and phenotype of the unknown plant. Offspring: 103 red long:101 red oval: 98 purple long: 100 purple oval
Red oval plant is RRL_ Offspring ratio for red:purple = 204:198, or ~1:1; Parent must be Rr Offspring ratio for long:oval = 302:100, or ~3:1; Parent must be Ll, Red oval plant was RRLl and crossed with RrLl (purple long)
3. In humans, red-green color blindness in inherited as an X-linked recessive trait. A woman with normal vision whose father is color-blind marries a male who has normal vision. Predict the color vision of their male and female offspring. Male offspring: color blind, normal vision Female offspring: all normal vision