– 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 the centromere, disc-shaped structures called kinetochores are present.
– Based on position of centromere, chromosomes are 4 types:
o Metacentric chromosome:
Middle centromere forming two equal arms of the chromosome.
o Sub-metacentric chromosome:
Centromere is nearer to one end forming one shorter arm and one longer arm.
o Acrocentric chromosome:
Centromere is close to its end forming one very short and one very long arm.
o Telocentric chromosome:
Terminal centromere. – Some chromosomes have non-staining secondary constrictions at a constant location. It is called a satellite.
– These are membrane-bound minute vesicles that contain various enzymes.
– Present in both plant and animal cells.
12 DIFFERENCE BETWEEN PLANT AND ANIMAL CELL
13 DIFFERENCE BETWEEN PROKARYOTIC AND EUKARYOTICS
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