What Exactly is a chromosome?
Chromosomes are the rod-shaped,
filamentous bodies present in the nucleus,
which become visible during cell division.
They are the carriers of the gene or unit of
Chromosome are not visible in active nucleus
due to their high water content, but are
clearly seen during cell division.
•Chromosomes were first described by
Strausberger in 1875.
•The term “Chromosome”, however was
first used by Waldeyer in 1888.
•They were given the name chromosome
(Chromo = colour; Soma = body) due to
their marked affinity for basic dyes.
•Their number can be counted easily only
during mitotic metaphase.
•Chromosomes are composed of thin
chromatin threads called Chromatin
•These fibers undergo folding, coiling and
supercoiling during prophase so that the
chromosomes become progressively
thicker and smaller.
•Therefore, chromosomes become readily
observable under light microscope.
•At the end of cell division, on the other
hand, the fibers uncoil and extend as
fine chromatin threads, which are not
visible at light microscope