The following points highlight the top two theories based on origin of mitochondria and chloroplasts. The theories are: 1. Endosymbiont Theory 2. Direct Filiation Theory. 1. Endosymbiont Theory: This theory is based on the similarities of chloroplasts and mitochondria with prokaryotic cells. These organelles possess their own genetic material (DNA) as well as the machinery for protein synthesis. According to [...]
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 [...]