Recitation Section 15 April 4-5, 2005 Diploid Genetics and Chromosomal Inheritance A. Diploid Genetics For each set of data below, determine the genotype of the parents in cross 1. Where it applies, indicate which phenotypes are dominant and which are recessive. 1. Mice I a) cross 1: red-eyed mouse ____________ X white-eyed mouse ____________ gives F1: all red-eyed cross 2: red-eyed F1 X red-eyed F1 gives F2: 36 red-eyed 13 white-eyed b) cross 1: long-eared mouse ____________ X short-eared mouse ____________ gives F1: 12 long-eared 10 short-eared cross 2: long-eared F1 X long-eared F1 gives F2: 36 long-eared 13 short-eared 2. Flowers cross 1: blue-flowered plant ____________ X white-flowered plant ____________ gives F1: all pale-blue-flowered cross 2: pale-blue F1 X pale-blue F1 gives F2: 27 blue 49 pale-blue 24 white3. Blood Type a) cross 1: person, type A blood ____________ X person with type B ____________ gives F1: all type AB blood cross 2: type AB F1 X type AB F1 gives F2: 2 type A 4 type AB 1 type B b) cross 1: type A blood ____________ X type B ____________ gives F1: 2 type A blood 3 type AB blood 1 type B blood 2 type O blood 4. Mice II cross 1: tail-less mouse ____________ X normal mouse ____________ gives F1: 10 tail-less 9 normal cross 2: tail-less F1 X tail-less F1 gives F2: 10 normal 21 tail-less 9 deadB. Chromosomes and Recombination 1. What is the physical basis of the genetic inheritance? 2. Why is sexual reproduction a powerful source of variation? 3. Why was it evolutionarily advantageous to develop the ability to recombine chromosomes? Think about the following question for next time (we will talk about it in Section 16): Recombination can occur anywhere along the length of the chromosome. However, we have been relying on the fact that genes are inherited as discreet units. How do we reconcile these two things? (Hint: think about what usually is the difference between two alleles of the same
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