Nucleus and Chromosomes Questions in English

(C) The provided diagram represents the structure of a chromosome.
Label $I$ points to the secondary constriction,which is a region of the chromosome other than the primary constriction (centromere).
Label $II$ points to the satellite,which is a small chromosomal segment separated from the main body of the chromosome by a secondary constriction.
Therefore,$I$ and $II$ indicate secondary constriction and satellite,respectively.

(A) $Acrocentric$: Chromosomes with the centromere situated near the end,resulting in one very short arm and one very long arm.
$Metacentric$: Chromosomes with the centromere at the center,forming two equal arms.
$Sub-Metacentric$: Chromosomes with the centromere slightly away from the center,resulting in one shorter arm and one longer arm.
$Telocentric$: Chromosomes with the centromere at the terminal end.

(D) The size of a typical mammalian cell nucleus is approximately $10^{-6} \text{ meter}$ ($1 \text{ } \mu\text{m}$ to $10 \text{ } \mu\text{m}$ range).
While the total length of $DNA$ contained within the nucleus is about $2.2 \text{ meters}$,the nucleus itself is a microscopic organelle.
Therefore,the correct order of magnitude for the size of the nucleus is $10^{-6} \text{ meter}$.

(D) The correct answer is $D$.
In the provided diagram of a chromosome,the part labelled as '$M$' represents the satellite.
$A$ satellite is a small chromosomal segment separated from the main body of the chromosome by a secondary constriction.
Chromosomes possessing this feature are known as $SAT$-chromosomes.

$(A)$ nucleosome is the fundamental structural unit of chromatin.
It consists of a segment of $DNA$ wrapped around a core of histone proteins.
The core particle is composed of an octamer of histone proteins $(H2A, H2B, H3, \text{ and } H4)$, around which approximately $146$ base pairs of $DNA$ are coiled.
Therefore, a nucleosome contains both $DNA$ and histones.

(A) The nucleolus is a non-membrane bound sub-organelle present inside the nucleus. It is the primary site for the transcription and processing of ribosomal $RNA$ $(rRNA)$ and the assembly of ribosomal subunits.