Question

Describe the structure of chromosome with a suitable diagram.

Answer 1

A chromosome consists of pellicle, matrix, chromonema, chromomere, centromere, secondary constriction and telomere.

• Pellicle: It is the outermost thin proteinaceous covering of the chromosome.

• Matrix: It is the liquid non-genetic achromatic ground substance of chromosome, having different types of enzymes, minerals, water, proteins, lipids, etc.

• Chromonema (single chromonemata): It is a highly coiled thread chromatin which is spread throughout the length of the chromosome or the chromatid. Each thread of chromonemata consists of a single long thread of DNA associated with histones. Sometimes, bead-like structures appear on the chromonema fibres. These fibres are called chromomere.

• Centromere: It is the area where the two chromatids are attached to each other. It consists of two proteins disc called kinetochores. The kinetochore is the actual site where the spindle fibres are attached to the chromosomes during the cell division.

• Secondary constriction: The chromosomal arms may contain other constrictions which are called secondary constrictions. These secondary constrictions are present near the chromosomal ends.

• Telomere: The tips of chromosomes are called telomeres which are rich in GT nucleotides. Telomere facilitates the attachment of chromosomes with the nuclear envelope.