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A Handbook of Biology

ÇHRØMØSØMËS:

A human cell has 2 m long thread of DNA distributed among its 46 (23

pairs) chromosomes.

Every chromosome has a primary constriction (centromere). On the

sides of centromere, disc shaped structures called kinetochores are

present.

Based on position of centromere, chromosomes are of 4 types:

Middle centromere forming two equal arms of the

chromosome.

Metacentric chromosome:

Sub-metacentric chromosome:

Centromere is slightly away from the middle of the

chromosome forming one shorter arm and one longer arm.

(NEET 2018)

Acrocentric chromosome:

Centromere is close to its end forming one very short and one

very long arm.

Telocentric chromosome:

It has a terminal centromere.

11.

Microbodies

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These are membrane bound minute vesicles that contain various

enzymes.

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Present in both plant and animal cells.