Answer: (3)
Chromosomes are thread-like structures woven together. Each chromosome is made of proteins and a single molecule of deoxyribonucleic acid (DNA). Chromosomes have been defined as bundles of tightly coiled DNA located within the nucleus of almost every cell in our body. This unique structure of chromosome keeps DNA tightly wrapped around spool-like proteins, named histones.
Functions of chromosomes
- The main function of chromosomes is to carry the genetic material from one generation to another.
- Chromosomes play an important role and act as a guiding force in the growth, reproduction, repair and regeneration process, which is important for survival.
- Chromosomes protect the DNA from getting tangled and damaged.
- Histone and non-histone proteins help in the regulation of gene expression.
- Spindle fibres 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.
Structure
Centromere or primary constriction or kinetochore, chromatids, chromatin, secondary constriction, telomere, chromomere, chromonema, and matrix are the eight components of a chromosome.
- The centromere, also known as the kinetochore, is the central constriction to which the chromatids or spindle fibres are linked. Its purpose is to allow chromosomal mobility during the anaphase stage of cell division.
- A chromosome is separated into two identical half strands and united by a centromere during cell division. Each half of the chromosome is linked to form a chromatid.
- Chromatin is a DNA and protein complex found in the nucleus of eukaryotic cells that creates chromosomes. To fit inside the nucleus, nuclear DNA is extremely compressed and wrapped around nuclear proteins.
- Secondary Constriction: It is present for nucleolar organisation in most cases.
- Telomere: Each chromosome’s terminal segment is known as the telomere. There are two copies of the Ach chromosome.
- Chromonema: The chromomeres are organised along a threadlike coiled filamentous structure.
- Chromomeres are the bead-like structures found on chromonema or threads. Along the length of the chromonema, they are organised in a row.
- Pellicle: The membrane that surrounds each chromosome is known as the matrix. Inside the pellicle, there is a jelly-like material called matrix. It is made up of non-genetic components.
