4. Genetic Mapping and Linkage

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.

The genetic distances between three genes (ab, nm, kf) were determined using a two-point mapping cross. Determine the sequence of the three genes. 

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  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?