The common point of attachment of all the arms of polytene chromosome is known as

$DNA$ 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

Chromatin was discovered by $...........$.

Match the chromosome types based on the position of the centromere as shown in the standard classification:

Column-$I$ (Type)	Column-$II$ (Description)
$1$. Metacentric	$a$. Terminal centromere
$2$. Sub-metacentric	$b$. Sub-terminal centromere
$3$. Acrocentric	$c$. Middle centromere
$4$. Telocentric	$d$. Slightly away from the middle

Chromosomes are made up of

The structure present on the chromosomes is: