The below mentioned article provides a short note on mitotic crossing over. Crossing over not only occurs during meiosis but also during mitosis. In individuals heterozygous for a gene producing a visible phenotype, somatic crossing over leads to the production of "twin spots" of dominant and recessive phenotypes. Mitotic crossing over was first discovered in Drosophila by Stern in 1936, [...]
In this article we will discuss about the molecular basis of crossing over. Any molecular model of crossing over must accommodate the explanation of the following phenomena: (a) Gene conversion, (b) Post-meiotic segregation, (c) Polarized conversion and (d) Negative interference. a. Gene Conversion: It is the unequal recovery of alleles in the region of exchange during genetic recombination in cases [...]
In this article we will discuss about the relationship between genetic and cytological crossing over. The exchange of homologous segments of chromatids between homologous chromosomes during meiosis was cytologically demonstrated by Stern in 1931 in D. melanogaster and by Creighton and McClintock in the same year in maize. Stern used stocks of D. melanogaster carrying chromosomal structural changes. These stocks [...]