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 [...]
The following points highlight the three main types of allopolyploidy. The types are: 1. Segmental Allopolyploidy 2. Genome Allopolyploidy 3. Auto-Allopolyploidy. Type # 1. Segmental Allopolyploidy: Some degree of homology (partial homology) may exist between some chromosome of one genome and those of the other genome. Therefore, in such polyploids both bivalents and multivalents are formed. This type of chromosome [...]
In this article we will discuss about:- 1. Origin and Occurrence of Autotetraploids 2. Chromosome Pairing and Chiasma Formation in Autotetraploids 3. Fertility 4. Genetics. Origin and Occurrence of Autotetraploids: Autotetraploids originate both spontaneously and can be experimentally induced; the various means of their origin are briefly described below: A. Spontaneous origin: (1) In diploid (2x) plants, sometimes a tetraploid [...]