Chromosomes are rod-like structures that consist only of DNA. True or False?
The correct answer and explanation is:
False.
Chromosomes are indeed rod-like structures, but they do not consist only of DNA. They are primarily made up of DNA and proteins, most notably histones. The DNA wraps around histones, forming nucleosomes, which further coil and fold to create the characteristic structure of chromosomes.
DNA is a long molecule that contains genetic instructions. For it to fit within the nucleus of a cell, it must be packaged in a highly organized manner. This organization begins when the DNA strands are coiled around histone proteins, forming nucleosomes, which resemble beads on a string. These nucleosomes are then further coiled and folded into more compact structures to form the chromosomes seen during cell division.
During cell division, chromosomes become highly condensed and take on their characteristic rod-like appearance. This condensation is crucial because it ensures that the DNA is properly distributed to the daughter cells. The proteins associated with chromosomes play various roles in maintaining the structure and function of the DNA. Histones help regulate gene expression and ensure the stability of the genome.
So, while chromosomes are made up of DNA, the statement that they consist only of DNA is incorrect. The presence of proteins, especially histones, is vital to the structure and function of chromosomes, enabling the efficient packaging and regulation of genetic material.