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, [...]
The following points highlight the five main types of trisomics which is a cell tissue or individual possessing the extra chromosome. The types are: 1. Primary Trisomics 2. Secondary Trisomics 3. Telocentric or Telosomic or Telotrisomics 4. Tertiary Trisomics 5. Compensating Trisomics. Type # 1. Primary Trisomic: In this type of trisomic, the extra chromosome is normal and completely homologous [...]
In this article we will discuss about the aneuploidy in animals. Aneuploidy of sex chromosomes and autosomes have been reported in several animals. Nondisjunction is major source of aneuploid gametes Sturtevant reported that trisomic for chromosome 4 (triplo-IV) in Drosophila melanogaster ABCDEFGH was fertile in the female sex. In mouse, trisomics were found to be sterile or semi-sterile, but their [...]