Problem 1. Cotton was cultivated for millennia as a source of fiber in the Old W

Question

Problem 1. Cotton was cultivated for millennia as a source of fiber in the Old World. The two most commonly cultivated species were Gossypium herbacium and G. arboreum. Both species have 2n 26 chromosomes. They differ from each other by a reciprocal translocation. Cotton was also cultivated by ancient civilizations in the New World. The two cultivated species were G. hirsutum and G. barbadense, each with 2n 52 chromosomes. A total of 26 wild species with 2n 26 chromosomes have been identified in Africa, South and Central America Australia, and the Middle East. Two wild species with 2n- 52 chromosomes have been identified, one with a limited range in northern Brazil and a second in Hawaii. What is the ploidy of the New World cotton cultivated cotton species G. hirsutum and G barbadense? A. monoploid B. diploid C. triploid D. tetraploid E. hexaploid F. octaploid Problems 2 - 3. In alfalfa, an autotetraploid, purple flowers are due to an allele (C1) that shows complete dominance to the recessive c/ allele. White flowers appear when the plants are nulliplex (ciCICici) whereas purple flowers will appear if at least one of the alleles is C1. A purple-flowered plant is crossed to a white- flowered plant. Half of the Fi progeny are purple-flowered and half are white-flowered 2. What is the genotype of the purple-flowered parent? A. CIcICICI B. CICIcici C. CjCICIc D. CICICIC 3. What proportion of purple-flowered progeny would be expected in the F2 generation if one of the purple-flowered Fi plants is self-pollinated? A. 0.125 B. 0.25 C. 0.375 D. 0.5 E. 0.75

Explanation / Answer

1. The ploidy of G.hirsutum and G.barbadense species of new world cotton is " Tetraploid ". 2. Genotype of purple - flowered parent is " C1C1c1c1 ". 3. The proportion of purple - flowered progeny of F2 generation is " 0.75 ".

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