In this article we will discuss about:- 1. Meaning of Chromosomes 2. Number of Chromosomes 3. Size 4. Chemical Composition 5. Functions 6. Special Types. Meaning of Chromosomes: Chromosomes are the most important constituents of the nucleus and were first observed by Holfmeister (1848) in pollen mother cell of Tradescantia and called it nuclear filaments. Chromosomes are filamentous bodies which [...]
In this article we will discuss about:- 1. Meaning of Crossing-Over 2. Example of Crossing Over in Drosophila 3. Theories 4. Mechanism 5. Kinds 6. Percentage 7. Cytological Evidence 8. Factors 9. Cytological Evidence 10. Significance 11. Interference and Coincidence. Meaning of Crossing-Over: The phenomenon of complete linkage occurs rarely since the linked genes tend to separate during meiotic divisions. [...]
The following points highlight the four main types of structural changes in chromosomes. The types are: 1. Deletion 2. Duplication 3. Translocations 4. Inversions. Structural Change: Type # 1. Deletion: Deletion refers to loss of a portion of segment from a chromosome. It is also known as deficiency. Deletions have been observed in Drosophila, maize, tomato, wheat and several other [...]