NCERT.UNIT 8.CELL:- THE UNIT OF LIFE

Chromosomes: 

CHROMOSOME

– 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:

SATELLITE CHROMOSOME / SAT CHROMOSOME / TELOMERE

Terminal centromere. – Some chromosomes have non-staining secondary constrictions at a constant location. It is called a satellite.

LAMP BRUSH CHRIOMOSOME AND POLYTENE CHROMOSOME

11. Microbodies

– 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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