When two heterozygotes are mated, the ratios of the offspring produced should be in a 1:2:1 ratio if normal Mendelian segregation is occurring. If one of the alleles is dominant, then the phenotypes observed should be present in a 3:1 ratio with the dominant phenotype more common than the recessive one. We can use an ?² goodness-of-fit test to test whether the ratio of offspring is indeed 3:1. Imagine a cross is performed and the number of offspring observed are 65 with the dominant phenotype and 35 with the recessive phenotype. Using the table of critical values shown, what is the conclusion of our test?
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$\begin{array}{c}\chi^{2} \text { critical values }\\\text { for } d f=2\\\begin{array}{ll}\text { Sig. level } & \text { Value } \\\hline 0.05 & 3.84 \\0.025 & 5.02 \\0.01 & 6.63\end{array}\end{array}$

Question

When two heterozygotes are mated, the ratios of the offspring produced should be in a 1:2:1 ratio if normal Mendelian segregation is occurring. If one of the alleles is dominant, then the phenotypes observed should be present in a 3:1 ratio with the dominant phenotype more common than the recessive one. We can use an ?² goodness-of-fit test to test whether the ratio of offspring is indeed 3:1. Imagine a cross is performed and the number of offspring observed are 65 with the dominant phenotype and 35 with the recessive phenotype. Using the table of critical values shown, what is the conclusion of our test?
?

\begin{array}{c}\chi^{2} \text { critical values }\\\text { for } d f=2\\\begin{array}{ll}\text { Sig. level } & \text { Value } \\\hline 0.05 & 3.84 \\0.025 & 5.02 \\0.01 & 6.63\end{array}\end{array}

Quizplus · Accepted Answer

The chi-square test statistic is calculated as follows: $\chi^2 = \frac{(65-75)^2}{75} + \frac{(35-25)^2}{25} = \frac{100}{75} + \frac{100}{25} = 1.33 + 4 = 5.33$. Since 5.33 is greater than the critical value of 3.84 at the 0.05 significance level, we reject the null hypothesis, suggesting that something other than usual Mendelian segregation is occurring.

When Two Heterozygotes Are Mated, the Ratios of the Offspring