We see in the previous two exercises that sprinters are more likely to have allele R and genotype RR versions of the ACTN3 gene, which makes these versions associated with fast-twitch muscles. Is there an association between genotype and gender? Computer output is shown for this chi-square test, using the control group in the study. In each cell, the top number is the observed count, the middle number is the expected count, and the bottom number is the contribution to the chi-square statistic. What is the p-value? What is the conclusion of the test? Is gender associated with the likelihood of having a €˜€˜sprinting gene€?

The gene ACTN3, which encodes a protein that functions in fast-twitch muscles. People can be classified according to which genotype of this gene they have, RR, RX, or XX, and also according to which genetic allele they have, R or X.

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RR RX XX Total Male 40 73 21 134 40.26 69.20 24.54 0.002 0.208 0.509 Female 147 88 57 292 87.74 150.80 53.46 0.001 0.096 0.234 Total 220 128 78 426 Chi-Sq = 1.050, DF = 2, P-Value = 0.592