Question

The ………………… is a primary constriction.
A. Telomere
B. Sarcomere
C. Chromomere
D. Centromere

Answer 1

Hint: Primary constriction can be seen when the chromosomes get narrower by getting condensed. It usually occurs in the metaphase during the division of the cell cycle. It is one of the 8 subparts of the chromosome structure. It is the basis by which two chromatids remain attached.

Complete answer:
Primary constriction is the basic centromere by which the early new chromatids (newly formed chromosomes) remain attached to each other.
Its capacity is to empower the development of the chromosome during the anaphase phase of the cell division.
In microscopy, stained chromosomes reveal how the primary constriction looks like.
It can be differentiated in the electron microscopy as the lightly stained region having the centromere in the specific position where both the arms are of equal propositional and condensed in nature that is known to be the primary constriction of the chromosome.
Primary constriction is present from the initial stage but with the succession of new and complicated stages secondary constriction occurs in telomeres, chromomena, and matrix.
Chromosome is the thread-like structure which is joint with a bead-like structure (centromere) in between.

The correct option is D.) Centromere.

Note: Chromosome consists of eight parts known to be as 1 – centromere or primary constriction 2 – chromatid 3- chromatin 4- secondary constriction 5 – telomere 6- chromomere 7- chromonema 8- matrix. These all get modified in the different progressive stages of cell cycle and chromosome division. These all can be seen in electron microscopy clearly.