Three loci, mitochondrial malate dehydrogenase that forms a and b (MDHa, MDHb), glucouronidase that has forms 1 and 2 (GUS1, GUS2), and a histone gene that has + and - variants(H+, H-), are located on chromosome #7 in humans. Assume that the MDH locus is at position 35, GUS at position 45, and H at position 75. A female whose mother was homozygous for MDHa, GUS2, and H+ and whose father was homozygous for MDHb, GUS1, and H- produces a sample of 1000 egg cells. Give the genotypes and expected numbers of the various types of cells she would produce. Assume no chromosomal interference.
Since, the MDH locus is at position 35, GUS at position 45, and H at position 75, GUS is in between MDH & H.
Distance between MDH & GUS = 10 map unit
Distance between GUS & H = 30 map unit.
Since % recombinants = map distance
Hence, for gene MDHa & GUS2 locus :
10 = No. of recombinants for crossing over between MDHa & GUS2 / 1000 * 100
Or, No. of recombinants for crossing over between MDHa & GUS2 = 100