The following points highlight the two main adaptational forms of chromosomes. The forms are: 1. Polytene Giant Chromosomes 2. Lampbrush Chromosomes. Form # 1. Polytene Giant Chromosomes: Polytene giant chromosomes are normal interphase chromosomes where homologues become paired and undergo several replications; all the copies so produced remain associated together. Polytene giant chromosomes are typically […]
In this article we will discuss about the molecular basis of crossing over. Any molecular model of crossing over must accommodate the explanation of the following phenomena: (a) Gene conversion, (b) Post-meiotic segregation, (c) Polarized conversion and (d) Negative interference. a. Gene Conversion: It is the unequal recovery of alleles in the region of exchange […]
The following points highlight the four main types of permanently specialized chromosomes. The types are: 1. Nucleolar Chromosomes 2. Sex Chromosomes 3. B Chromosomes 4. Chromosomes with Diffuse or Multiple Centromeric Regions. Permanently Specialized Chromosomes: Type # 1. Nucleolar Chromosomes: The chromosome forming the nucleolus (plural = nucleoli) is called the nucleolar chromosome. Normally one […]
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