In this article we will discuss about:- 1. Classification of Haploids 2. Origin of Haploids 3. Meiosis. Classification of Haploids: According to their cytological features, haploids have been classified into different types (Fig. 17.1), a brief description of which is given below. I. Euhaploid: The chromosome number of such a haploid is an exact multiple of one of the basic [...]
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 [...]