Identify $X$ from the given figure:

Describe the composition, structure, and types of chromosomes.

Who coined the term "chromosome"?

........ is present in a higher amount in the dark band of a polytene chromosome.

In which structure is the 'beads-on-a-string' appearance observed?

$DNA$ genetic material occurs by itself in lower organisms and combined with proteins as nucleoproteins in higher organisms. The nucleoprotein is organized in higher forms to form