In this article we will discuss about:- 1. Introduction to Crossing Over of Genes 2. Factors Affecting Crossing Over of Genes 3. Cytological Basis of Crossing Over 4. Molecular Mechanism Crossing Over 5. Hybrid DNA Models of Crossing Over. Contents: Introduction to Crossing Over of Genes Factors Affecting Crossing Over of Genes Cytological Basis of Crossing Over of Genes Molecular [...]
The following points highlight the four theories proposed for the mechanism of crossing over. The theories are: 1. Janssen's Classical Theory 2. Belling's Copy Choice Theory 3. Uhl's Theory 4. Darlington's Theory of Crossing Over. Theory # 1. Janssen's Classical Theory: Janssen (1909) believed that prior to the formation of chiasmata the homologous maternal and paternal chromosomes come in pair [...]
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 [...]