In this article we will discuss about:- 1. Meaning of Meiosis 2. Stages of Meiosis 3. Duration 4. Significance. Meaning of Meiosis: Chromosome number remains constant between the generations in asexually reproducing organisms since reproduction in them is based on mitosis. But in most species sexual reproduction does take place; it involves fertilization, i.e. fusion of male and female gametes. [...]
The following points highlight the four main hypothesis proposed for the mechanism of crossing over. The hypothesis are: 1. The Classical and Neo-Classical Hypotheses 2. Partial Chiasma Type Theory 3. Belling's Hypothesis 4. Copy-Choice Hypothesis. Mechanism of Crossing Over: Hypothesis # 1. The Classical and Neo-Classical Hypotheses: The classical hypothesis of crossing over was proposed by Sax in 1932; it [...]
In this article we will discuss about:- 1. Types of Chromosome Pairing 2. Factors Affecting Chromosome Pairing 3. Significance 4. Molecular Basis. Types of Chromosome Pairing: Chromosome pairing may be divided into three main types, viz., primary pairing, secondary association and non-homologous association, which may be further classified (Fig. 11.1). Primary Pairing: Primary pairing is observed at interphase, mitosis [...]