In flower beetles, pygmy (py) is recessive to normal size (py + ), and red color (r) is recessive to brown (r + ). A beetle heterozygous for these characteristics was test-crossed to a beetle homozygous for pygmy and red. The following are progeny phenotypes from this testcross. $$\begin{array} { l l r }
p y ^ { + } & r ^ { + } & 180 \
p y ^ { + } & r & 22 \
p y & r ^ { + } & 19 \
p y & r & 191 \
\text { Total } && 412
\end{array}$$ Carry out a series of chi-square tests to determine if there is equal segregation of alleles at the py locus.
- What is the correct chi-square value and how many degree(s) of freedom should be used in its interpretation?
A) 0.16 with one degree of freedom
B) 0.16 with three degrees of freedom
C) 0.48 with one degree of freedom
D) 0.48 with two degrees of freedom
E) 4.56 with one degree of freedom

Question

In flower beetles, pygmy (py) is recessive to normal size (py + ), and red color (r) is recessive to brown (r + ). A beetle heterozygous for these characteristics was test-crossed to a beetle homozygous for pygmy and red. The following are progeny phenotypes from this testcross. $$\begin{array} { l l r } 
p y ^ { + } & r ^ { + } & 180 \
p y ^ { + } & r & 22 \
p y & r ^ { + } & 19 \
p y & r & 191 \
\text { Total } && 412
\end{array}$$ Carry out a series of chi-square tests to determine if there is equal segregation of alleles at the py locus.
- What is the correct chi-square value and how many degree(s) of freedom should be used in its interpretation?
A) 0.16 with one degree of freedom
B) 0.16 with three degrees of freedom
C) 0.48 with one degree of freedom
D) 0.48 with two degrees of freedom
E) 4.56 with one degree of freedom

Quizplus · Accepted Answer

The correct chi-square value is 0.16 with one degree of freedom. This is because the expected ratio of pygmy to normal-sized beetles is 1:1, and the observed ratio is very close to this. The chi-square test is used to determine whether the observed ratio is significantly different from the expected ratio. In this case, the chi-square value is 0.16, which is not significant at the 0.05 level. This means that there is no evidence to reject the hypothesis that the alleles at the py locus are segregating equally.

In Flower Beetles, Pygmy (Py) Is Recessive to Normal Size