11TheGeneTicsRevoluTionPROBLEMSIn each chapter, a set of problems tests the reader’s comprehension of the concepts in the chapter andtheir relation to concepts in previous chapters. Each problem set begins with some problems based onthe figures in the chapter, which embody important concepts. These are followed by problems of a moregeneral nature.WORKING WITH THE FIGURES1.If the white-flowered parental variety in Figure 1-3 were crossed to the first-generation hybrid plantin that figure, what types of progeny would you expect to see and in what proportions?Answer: You would get a 1:1 ratio of purple to white. This is because the first-generation hybridplant has one copy of the purple allele and one copy of the white allele, and as a result, 50 percent ofthe gametes would carry the purple allele and 50 percent of the gametes would carry the white allele.The white-flowered parental variety has two copies of the white allele, and all the gametes producedfrom the white plant will carry the white allele. Hence, a cross between the two would produce a 1:1ratio of purple to white.Hybrid plantP/p¥white plantp/pGametes50%P50%p¥100%p50%P/p: 50%p/pPurple:white2.In Mendel’s 1866 publication as shown in Figure 1-4, he reports 705 purple (violet) floweredoffspring and 224 white-flowered offspring. The ratio he obtained is 3.15:1 for purple:white. Howdo you think he explained the fact that the ratio is not exactly 3:1?Answer: This depends on the sample size. When the sample size was large, the proportions wereclose to 3:1 (e.g., for round and wrinkled seeds the ratio was 2.95:1 and the total population sizeIGA 11e SM Ch 01.indd111/12/142:05 PMPreview Mode
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