In a series of two-point mapping crosses involving five genes located on chromosome II in Drosophila, the following recombinant (single-crossover) frequencies were observed:

In another set of experiments, a sixth gene, d, was tested against b and pr:

Predict the results of two-point mapping between d and c, d and vg, and d and adp.

Genes A, B, C, D, and E are linked on a chromosome and occur in the order given.

The test cross Ae/aE x ae/ae  indicates the genes recombine with a frequency of 28%. If 1000 progeny are produced by this test cross, determine the number of progeny in each outcome class.

Genes A, B, C, D, and E are linked on a chromosome and occur in the order given.

Previous genetic linkage crosses have determined that recombination frequencies are 6% for genes A and B, 4% for genes B and C, 10% for genes C and D, and 11% for genes D and E. The sum of these frequencies between genes A and E is 31%. Why does the recombination distance between these genes as determined by adding the intervals between adjacent linked genes differ from the distance determined by the test cross?

Colored aleurone in the kernels of corn is due to the dominant allele R. The recessive allele r, when homozygous, produces colorless aleurone. The plant color (not the kernel color) is controlled by another gene with two alleles, Y and y. The dominant Y allele results in green color, whereas the homozygous presence of the recessive y allele causes the plant to appear yellow. In a testcross between a plant of unknown genotype and phenotype and a plant that is homozygous recessive for both traits, the following progeny were obtained:

colored, green: 88

colored, yellow: 12

colorless, green: 8

colorless, yellow: 92

Explain how these results were obtained by determining the exact genotype and phenotype of the unknown plant, including the precise arrangement of the alleles on the homologs.

In the cross shown here, involving two linked genes, ebony (e) and claret (ca), in Drosophila, where crossing over does not occur in males, offspring were produced in a 2 + : 1 ca : 1 e phenotypic ratio:

These genes are 30 units apart on chromosome III. What did crossing over in the female contribute to these phenotypes?

In a series of two-point mapping crosses involving five genes located on chromosome II in Drosophila, the following recombinant (single-crossover) frequencies were observed:

Given that the adp gene is near the end of chromosome II (locus 83), construct a map of these genes.

In Drosophila, a cross was made between females—all expressing the three X-linked recessive traits scute bristles (sc), sable body (s), and vermilion eyes (v)—and wild-type males. In the F₁, all females were wild type, while all males expressed all three mutant traits. The cross was carried to the F₂ generation, and 1000 offspring were counted, with the results shown in the following table.

No determination of sex was made in the data.

Determine the sequence of the three genes and the map distances between them.

In Drosophila, a cross was made between females—all expressing the three X-linked recessive traits scute bristles (sc), sable body (s), and vermilion eyes (v)—and wild-type males. In the F₁, all females were wild type, while all males expressed all three mutant traits. The cross was carried to the F₂ generation, and 1000 offspring were counted, with the results shown in the following table.

No determination of sex was made in the data.

Using proper nomenclature, determine the genotypes of the P₁ and F₁ parents.

Another cross in Drosophila involved the recessive, X-linked genes yellow (y), white (w), and cut (ct). A yellow-bodied, white-eyed female with normal wings was crossed to a male whose eyes and body were normal but whose wings were cut. The F₁ females were wild type for all three traits, while the F₁ males expressed the yellow-body and white-eye traits. The cross was carried to an F₂ progeny, and only male offspring were tallied. On the basis of the data shown here, a genetic map was constructed.

Could the F₂ female offspring be used to construct the map? Why or why not?