Week 7 Discussion Questions SP24

Discussion Questions Week 7 Questions SP23 4. Suppose that a geneticist discovers a new mutation in Drosophila melanogaster that causes the flies to shake and quiver. She calls this mutation quiver , qu , and determines that it is an autosomal recessive mutation. She wants to determine whether the gene encoding quiver is linked to the recessive gene for vestigial wings , vg . She crosses a fly homozygous for quiver and wild type wings with a fly homozygous for vestigial wings and wild type for behavior. She then uses the resulting F 1 females in a testcross. She obtains the flies from this testcross. Test the hypothesis that the genes  quiver  and  vestigia l assort independently by calculating the chi-square value,  𝑋 2 , for this hypothesis. Use the Chi-square Test for Independence (using a contingency table) . Provide the  𝑋 2  to one decimal place. Then look up the p-value for 1 degree of freedom, and interpret it P value indicates that the difference between the observation and the expected number of progeny would be statistically significant. So in this case we would be rejecting the this. 5. In Drosophila melanogaster , black body ( b ) is recessive to gray body ( b + ), purple eyes ( pr ) are recessive to red eyes ( pr + ), and vestigial wings ( vg ) are recessive to normal wings ( vg + ). The loci encoding these traits are linked, with the map distances shown in the image. The interference among these genes is 0.5. A fly with a black body, purple eyes, and vestigial wings is crossed with a fly homozygous for a gray body, red eyes, and normal wings. The female progeny are then crossed with males that have a black body, purple eyes, and vestigial wings. If a total of 1000 progeny are examined, determine the expected number of offspring that result from each crossover event. (Problem continued on next page.) Phenotype Number of flies 𝑣𝑔 +   𝑞𝑢 + 99 vg qu 97 vg  𝑞𝑢 + 224 𝑣𝑔 +  qu 230