Structure of Polytene Chromosomes
Polytene chromosomes have a structure that sets them apart from regular chromosomes. The unique structure including their giant size, banding pattern, chromomeres, and endoreplication, help in performing genetic research.
- Giant Size: Polytene chromosomes are larger than regular chromosomes. Their giant size results from the accumulation of multiple chromatids within a single nucleus due to the process of endoreplication.
- Banding Pattern: One of the most distinctive features of polytene chromosomes is a characteristic banding pattern. The banding pattern consists of alternating dark and light bands, each representing different levels of chromatin condensation.
- Chromomeres: The dark bands in the banding pattern are called chromomeres. Chromomeres represent regions of tightly packed and condensed chromatin. These regions typically correspond to areas of low activity.
- Interbands: The light bands in the banding pattern are referred to as interbands. Interbands represent regions of decondensed and active chromatin. These areas are involved in cellular processes.
- Puffs: Certain regions of polytene chromosomes show swellings or puffs. Puffs are areas where the chromatin is decondensed. Puffs are associated with regions of active gene expression and they are visible as expanded portions of the chromosome.
- Replication Bridges: During DNA replication in polytene chromosomes, multiple replication forks are initiated, resulting in the synthesis of many copies of DNA strands. The synthesized DNA strands remain associated, forming structures known as replication bridges.
Polytene Chromosome: Diagram, Structure & Functions
Polytene Chromosomes are specialized structures found in the nuclei of eukaryotic cells, characterized by their different banding pattern, and play a crucial role in understanding chromosomal organization, and cellular function. The unique structure of polytene chromosomes sets them different from the typical chromosomes found in most cells. They are also known as silvery gland chromosomes and unlike the typical chromosomes, polytene chromosomes undergo a process known as endoreplication, where DNA replication occurs without further cell division.
Table of Content
- What is the Polytene Chromosome?
- Polytene Chromosome Diagram
- How Polytene Chromosome Formed?
- Structure of Polytene Chromosomes
- Functions of Polytene Chromosomes
- Importance of Polytene Chromosomes
- Conclusion