Chromosomes are the genetic material present in all the cells. They are present in the nucleus of a eukaryotic cell. They are a thread-like structure. Each chromosome of a eukaryotic cell contains DNA and associated proteins, known as histone proteins. They are responsible for hereditary traits and passed from parents to offspring from one generation to another. Scientists have given this name chromosomes as they are stained using specific dyes, chroma means color, and soma means body.
Structure of Chromosomes
A chromosome has generally 8 parts; They are:
- Centromere or Kinetochore: It is the primary constriction at the center to which the chromatids or spindle fibers are attached. Its function is to enable the movement of the chromosome during the anaphase stage of cell division.
- Chromatid: During cell division, a chromosome is divided into 2 identical half strands joined by a centromere. A chromatid is each half of the chromosome joined. Each chromatid contains DNA and separates at Anaphase to form a separate chromosome. Both chromatids are attached by the centromere.
- Chromatin: It is a complex of DNA and proteins that forms chromosomes within the nucleus of eukaryotic cells. Nuclear DNA is highly condensed and wrapped around nuclear proteins to fit inside the nucleus. In other words, it is not present as free linear strands. The chromatin consists of DNA, RNA, and protein.
- Secondary Constriction: It is generally present for the nucleolar organization.
- Telomere: Telomere is the terminal region of each side of the chromosome. Ach chromosome has 2
- Chromonema: It is a threadlike coiled filamentous structure along which chromomeres are arranged. Chromonema controls the size of the chromosome and it acts as a site of gene bearing.
- Chromomeres: These are the bead-like structures present on threads or chromonema. These are arranged in a row along the length of chromonema. The number of chromosomes is constant and it is responsible for carrying the genes during cell division to the next generation.
- Matrix: Pellicle is the membrane surrounding each of the chromosomes. Matrix is the jelly-like substance present inside the pellicle. It is formed of non-genetic materials.
Functions of Chromosomes
- They carry the genetic material from one generation to another generation.
- Play an important role and act as a guiding force in the growth, reproduction, repair, and regeneration process, which is important for their survival
- They protect the DNA from getting tangled and damaged
- Histone and non-histone proteins help in the regulation of gene expression
- Spindle fibers attached to the centromere help in the movement of the chromosome during cell division
- Each chromosome contains thousands of genes that precisely code for multiple proteins present in the body.