Gene G recombines with gene T at a frequency of 7%, and gene G recombines with gene R at a frequency of 4%.


Draw two possible genetic maps for these three genes, and identify the recombination frequencies predicted for each map.

True or False:Recombination frequencies are never greater than 50%

Using the following data collected from a test cross, calculate the recombination frequency.

In a diploid species of plant, the genes for plant height and fruit shape are syntenic and separated by 18 m.u. Allele D produces tall plants and is dominant to d for short plants, and allele R produces round fruit and is dominant to r for oval fruit.

Give the same information for a plant with the genotype Dr/dR.

Genes A, B, and C are linked on a chromosome and found in the order A–B–C. Genes A and B recombine with a frequency of 8%, and genes B and C recombine at a frequency of 24%. For the cross a⁺b⁺c/abc⁺ × abc/abc, predict the frequency of progeny genotypes. Assume interference is zero.

Gene G recombines with gene T at a frequency of 7%, and gene G recombines with gene R at a frequency of 4%.

Assuming that organisms with any desired genotype are available, propose a genetic cross whose result could be used to determine which of the proposed genetic maps is correct.

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.