LIFE 102 Lecture Notes - Lecture 17: Down Syndrome, Covalent Bond, Trisomy
Document Summary
Cross to test for linkage of a + b genes. Aabb can make ab, ab, ab, ab genes. If they"re on different chromosomes and they"re not linked if you get equal probability of each resulting genotype. Because of the chiasmata that form in meiosis. Prophase i: recombination occurs between parental and maternal chromosomes. Crossover between genes a and b may give recombinants (see figure 15. 10) During meiosis in a double homozygote, get parental types and some recombinants, more when the genes are further apart. Recombination frequency = (# recombinants) / (# total offspring). The percentage = number of map units apart. The recombination frequency reflects the distance between two genes (greater distance. For example, if you get 1-% recombinants, two genes are 10 map units (mu) apart. (in centimorgans named after morgan). The smaller the percentage, the closer they are together on the chromosome.
