PracticeMT1_Key

PracticeMT1_Key - GENETICS BICD100 Fall 2005 MIDTERM 1...

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GENETICS BICD100 Fall 2005 Reinagel MIDTERM 1 MENDELIAN GENETICS PRACTICE TEST ANSWER KEY 1. You perform a cross between a long-eared mouse and a short-eared mouse of unknown genotypes. You obtain 12 long-eared mice and 10 short-eared mice in the progeny (F1). You cross the long-eared F1 progeny with one another and you get 77 long-eared mice and 23 short-eared mice in the F2 generation. 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: 77 long-eared 23 short-eared a) Using letters of your own choosing, state the most likely genotypes of the original two parents, stating which phenotypes are dominant and using a capital letter for the dominant alleles. A = long ear, dominant a = short ear, recessive Parents are Aa (long) x aa (short) b) Based on your answer to part (a), state the expected genotypes of the F1, and in what ratio they should occur Aa aA a a a a a a so the F1 genotypic ratio should be 1 Aa : 1 aa c) Based on your answers to parts (a) and (b), state the expected genotypes of the F2 (offspring from cross 2), and in what ratio they should occur In cross 2, the long-eared F1 progeny were crossed to each other, so Aa x Aa AA A A a a a a The expected genotypic ratios are: 1 AA : 2 Aa : 1 aa
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GENETICS BICD100 Fall 2005 Reinagel d) State the phenotype of each genotype in the F2 and use this to predict the phenotypic ratios in the F2 generation 1 AA long 2 Aa long Æ 3 long : 1 short is the phenotypic ratio 1 aa short Alternatively: Draw the punnet square, Draw the segregation tree, or write out the probabilities and use the product and sum rules. 2. You cross a wingless fly with a normal fly and obtain 23 wingless and 27 normal flies in the F1 progeny. To test your hypothesis about the mode of inheritance you then cross wingless F1 progeny by one another, and you obtain 19 normal flies and 44 wingless flies in the F2 generation. cross 1: wingless fly X normal fly gives F1: 23 wingless 27 normal cross 2: wingless F1 X wingless F1 gives F2: 19 normal 44 wingless a) Using letters of your own choosing, state the most likely genotypes of the original two parents, stating which phenotypes are dominant and using a capital letter for the dominant alleles.
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PracticeMT1_Key - GENETICS BICD100 Fall 2005 MIDTERM 1...

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