The below mentioned article provides a note on nullisomy in chromomes. The cell, tissue or organism in which both the homologues of a chromosome are missing from the somatic chromosome complement is called nullisomic (2n-2), and the condition is called nullisomy. If two pairs of homologous chromosomes are absent, the cell, tissue or organism is known as double nullisomic (2n-2-2). [...]
In this article we will discuss about:- 1. Distribution and Occurrence of Polyploidy 2. Classification of Polyploidy. Distribution and Occurrence of Polyploidy: Polyploidy is wide spread in plant kingdom but is less common in animal kingdom. Darlington and Janaki-Ammal in 1945 and Stebbins in 950 estimated that polyploids make up 30 to 35% of Angiosperms. In certain families, very high [...]
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 [...]