A researcher is attempting to determine the inheritance pattern exhibited by the

Question

A researcher is attempting to determine the inheritance pattern exhibited by the alleles determining shell color in a species of freshwater snail. The trait is known to be controlled by alleles at a single autosomonal locus, and the researcher hypothesizes that there are two alleles, one for brown which is completely dominant to the allele for yellow. A mating between a brown-shelled snail and a yellow-shelled snail, both from pure-breeding lines, produces progeny that are brown shelled. The mating of two F1 snails produces an F2 consisting of 54% with yellow shells and 46% with brown shells. The researcher wishes to carry out a X^2 test on F2 outcome and deicides to compare his observed values of 54% and 46% with a ratio of 1:1 which is close to the observed results> The resultant X2 value is small and, because of that, the researcher records in his notebook that "the deviation is definetly due to chanec" and that "the hypothesis must be correct" -

THE RESEARCHER HAS MADE A NUMBER OF ERRORS IN USING THE X2 TEST. IDENTIFY AT LEAST 3 OF THESE ERRORS..(Thank you!)

Explanation / Answer

Chi square value = (o-e)2/ e

let the total value be 100. Expected values are 50 yellow and 50 brown shells. Observed values are 54 yellow and 46 brown.

Chi square value for yellow = (54-50)^2/ 50 = 16/50 = 0.32

Chi square value for brown= (46-50^2/ 50 = 16/50 = 0.32

X^2 = 0.32+0.32 = 0.64

degree of freedom = 1

Looking at the X^2 distribution table, p value comes out to be between 0.15 and 0.46

If p>0.05, then null hypothesis is rejected. So, null hypothesis should be rejected over here.

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