The following points highlight the four main hypothesis proposed for the mechanism of crossing over. The hypothesis are: 1. The Classical and Neo-Classical Hypotheses 2. Partial Chiasma Type Theory 3. Belling's Hypothesis 4. Copy-Choice Hypothesis. Mechanism of Crossing Over: Hypothesis # 1. The Classical and Neo-Classical Hypotheses: The classical hypothesis of crossing over was proposed by Sax in 1932; it [...]
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 [...]