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Introductory Animal Genetics
Animal Science 221

X2 Test for Independence

Andersson, L. and K. Sandberg, 1982. A linkage group composed of three coat color genes and three serum protein loci in horses. Journal of Heredity 73:91.

The roan coat color in horses is produced by an allele, Rn, that in the heterozygous, Rnrn, dilutes the appearance of color by the intermingling of white hairs among those with color. The homozygous RnRn is lethal.

The serum protein esterase has among its codominant alleles, EsF and EsI. Progeny of a particular sire dihybrid at the roan and esterase locus, EsFEsIRnrn, was mated to nonroan mares. The distribution of progeny receiving the four different gametes for this dihybrid was:

Sire gamete # Progeny Expected number What is the expected number for each?
(Round to the nearest hundreth.)
EsFRn       19
EsIRn 26
EsFrn 29
EsIrn 17
91

Calculate the x2 for each of the following. Please give your answer to three significant figures.

A) The three degree of freedom x2 for the progeny distribution considering both loci jointly:

x23 =  

B) The x2 for the one-to-one ratio at the esterase locus:

x21 =  

C) The x2 for the one-to-one ratio at the roan locus:

x21 =  

D) The x2 for independence of the esterase and roan locus.

x21 =  



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