MT1_FullKEY

# MT1_FullKEY - BIS101-002/Draper Midterm 1 KEY (from Form A)...

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BIS101-002/Draper Spring, 2011 Midterm 1 KEY (from Form A) Questions 1-4: Charcot-Marie-Tooth disease is a progressive neuronal disordered that is caused by mutations that affect the function of neuronal proteins, some of which are involved in maintenance of the myelin sheath that wraps around axons. One such recessive mutation disrupts the function of the connexin 32 gene located on the X- chromosome. Answer the following questions using the pedigree below (X A = wild-type, X a = mutant). Knows and assumptions: I1 = X A Y, all people marrying in to the pedigree are WT (X A Y men and X A X A women). 1. (4 pts.) What is the genotype of II2? a. X A Y : Males gets there single X from mom, which in this case is X A X A 2. (4 pts.) What is the genotype of II4? b. X A X a :Females receive 1 X from dad and 1 X from mom. In this case mom will contribute X A and dad will contribute X a . 3. (5 pts.) If IV1 and IV2 have a child, what is the probability that it will be an affected boy? d. 1/16: Prob. that III4 is X A X a =1/2; Prob. that IV is X A X a =(1/2)(1/2)=1/4; Prob. that son will be XaY =(1/2 Y) from Dad (1/2 X a ) from Mom (1/4 that Mom is X A X a ) = 1/16 4. (5 pts.) If IV1 and IV2 have a child, what is the probability that it will be an affected girl? a. 0 : II2 receives his single X from mom so there is a 0% probability that this side of the lineage will segregate X a . Thus, IV1 is X A Y. Questions 5-9: The cross is Rr;Pp;Ii X Rr;Pp;Ii 5. (4 pts.) What is the expected proportion of progeny that will be homozygous for all three recessive traits? c. 1/64

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## This note was uploaded on 04/05/2012 for the course BIS 101 taught by Professor Simonchan during the Spring '08 term at UC Davis.

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MT1_FullKEY - BIS101-002/Draper Midterm 1 KEY (from Form A)...

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