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Unformatted text preview: Chapter 14 245 of both genes must lie within the deleted region—between A2-3 and D2-3. Deletion B, pseudodominant for henna, indicates that henna lies between C2-3 and E4—F1. Combining the results for Deletions A and B, henna must be between C2-3 and D2-3. Because Deletion B is javelin+, javelin must be located between A2-3 and C2-3 (the part of Deletion A that is not removed in Deletion B). Deletions C and D tell you that the henna gene cannot lie to the right of bands D2-3 on the figure in the text, delimiting henna to the interval between C2-3 and D2-3. Inversions do not remove genes, they just relocate them. Therefore, if the inversion is made in a wild-type chromosome, the inverted homolog will have the wild—type alleles for all of the genes. Inversion B gives the expected result, and does not help locate either of the two genes. Inversion A, however, has a mutant javelin phenotype, indicating that there is a mutant allele of javelin on the inverted homolog. Thus, the javelin gene was broken by the inversion, so javelin is located in band 65A6. (This is consistent with the region containing javelin determined from the deletions above.) Very few Drosophila genes extend beyond one band, so we can assume that A6 is the location of javelin. In summary, the javelin gene is in band 65A6 and the henna gene is between 65C2-3 and 65D2-3. . 14-9. The genotype of the female is: I? z] W+R spl+ y+ 21 w+R spl+ y z] w+ R spl y z] w+ R spl a. The remainder of the male progeny (76,671) are the parental types, so they will be y+ z] w+R spl+ / Y (zeste) and y zl w+R spl / Y (yellow zeste split). b. Classes A and B are a reciprocal pair of products. They are the result of crossing-over anywhere between the y and spl genes resulting in the reciprocal classes: y+ 21 w+R spl / Y (zeste split) and y z] w+R sler / Y (yellow zeste). c. Remember that w+R allele is really a tandem duplication of the w‘L gene and that the zeste eye color depends on having a mutant 21 allele in a genome that also contains two or more copies of w+. Classes C and D are the result of mispairing and unequal crossing-over between the two copies of the w+ gene. The misalignment can occur in two different ways, see the figure ...
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