Problem Set 5 Key

# Problem Set 5 Key - BICD100 FA2011 Problem Set#5 Mapping...

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BICD100 FA2011 Problem Set #5: Mapping with DNA markers, LOD scores, bacterial genetics (Pedigree and data not shown in key – see original problem set) 1.) The pedigree above shows the pattern of inheritance of a rare, hereditary form of deafness in a human family (assume that this trait is fully penetrant). PCR is carried out on DNA samples from all individuals in the pedigree to amplify a microsatellite marker on chromosome 10. a. Does the marker appear to be linked to the deafness gene? If so, estimate the map distance as accurately as possible based on the information provided. Trait is autosomal dominant. 1, 5 and 8 can make recombinant gametes that are informative; each of their children could potentially inherit one recombinant chromosome (4,5,7,8,12,13,14,15,16,17,18). Of 11 potentially recombinant chromosomes, one is recombinant (in individual 13) -> 9 cM. b. Calculate the LOD score representing the likelihood that this marker is linked to the deafness gene at the distance you indicated in a. LOD score for 9 cM = log 10 [(probability of linkage at 9 cM)/ (probability of no linkage)] = log 10 [(0.455 10 x 0.045)/(0.25) 11 ] = log 10 71.9 = 1.857 c. Is the data sufficient to draw a conclusion regarding linkage between this marker and the deafness gene? LOD score of > 3.0 is considered sufficient evidence of linkage, so no, this data is not sufficient. d. Do you expect the LOD score calculated from this data for a higher degree of linkage (that is, a smaller distance than what you indicated in a) to be higher or lower than the LOD score you calculated in part c? Lower. The LOD score peaks at the linkage value corresponding to the observed frequency of

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Problem Set 5 Key - BICD100 FA2011 Problem Set#5 Mapping...

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