PS01-Solutions

# PS01-Solutions - Genetics 320 Problem Set One Solutions 1(1...

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Genetics 320, Problem Set One Solutions 1 (1 point) :I f Pr( A, B )=0 . 15 , Pr( A )=0 . 2 and Pr( B )=0 . 4 , (a) What is the conditional probability of B given A ? Pr(A,B)/P(A) = 0.15/0.2 = 0.75 (b) What is the conditional probability of A given B ? Pr(A,B)/P(B) = 0.15/0.4 = 0.375 2 (2 points) : Suppose the frequency of a disease in the population is 0.005 and the relative risk for this disease (among sibs) is 35. (a) What is the probability that you have this disease given that your sib does? RR · K =35 · 0 . 005=0 . 175 (b) What is the expected frequency of two-sib families where both sibs have the disease? RR · K 2 =35 · 0 . 005 2 =0 . 000875 (c) Suppose we look at 1,000 randomly-chosen two-sib families. What is the probability that we will observe no families where both sibs have the disease? Pr(none) =(1 - 0 . 000875) 1000 =0 . 41670 . 3 (1 point) : Consider ﬁve offspring from a pair of Aa parents. What is the probability that no offspring are aa ? That all ﬁve are aa ? Pr(0) = (1 - p ) 5 =(3 / 4) 5 =0 . 237 , Pr(5) = ( p ) 5 =(1 / 4) 5 =0 . 00097 4 (1 point) : The Binomial distribution appears frequently in genetics and gives the proba- bility of k successes in n trials, given that the success probability per trial is p ,as Pr( k

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## This note was uploaded on 12/09/2009 for the course ECOL UNIVERSITY taught by Professor Walsh during the Spring '09 term at Arizona.

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PS01-Solutions - Genetics 320 Problem Set One Solutions 1(1...

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