Genetic Linkage and Three-Point Mapping - 07

what occurs at the chiasma during meiosis?

• crossing over

• physical exchange of genetic information

what occurs during mitosis?

• one cell division = two daughter cells

• one premeiotic S phase per cell division

• no pairing of homologs, no crossovers

• centromeres divide at anaphase

• daughter cells genotypes identical with parental genotype

what occurs during meiosis?

• two cell divisions resulting in four daughter cells

• chromosome number halved

• one premeiotic phase for both cell divisions

• full synapsis of homologs at prophase I

• at least one crossover per homologous pair

• centromeres do not divide at anaphase I, but do at anaphase II

• promotes variation among the products of meiosis

what is a three point cross?

• resembles Morgan’s two point cross using Drosophila, but uses a stock with 3 mutants crossed to the wild type

• uses the proportion of recombinants to infer the position of genes on chromosomes