BIOL 2000 Lecture Notes - Karyotype, Mendelian Inheritance, Centimorgan
Document Summary
Linked alleles tend to be inherited together. Morgan suggested that crossing over produces allelic combinations that are different from the meiotic input (recombinants) Morgan suggested that chromosomes break and re-join during pairing, and that chiasmata are visual evidence of that event. If we do not know that genes are linked separate gene pairs with . : pr/pr+ . vg/vg+ If we know genes are independently assorting (unlinked), separate gene pairs with ; : a/a+ ; b/b+ Morgan proposed that crossing over between chromatids, not chromosomes. A second division segregation pattern in a fungal octad demonstrates that crossing over must be between chromatids. Multiple crossovers can include more than two chromatids to generate multiple types of linear tetrads: centrosome decides where the crossing over occurs, can occur on both sides of centromere. Morgan"s result: if test crosses were done involving different pairs of genes, saw different ratios of parental: recombinant.
