Question

what are chromosomes? explain how in sexually reproducing organism the number of chromosome in the progeny is maintained

Answer 1

Chromosomes are thread like particles present in nucleus.They are of 4 types.
1) metacentric
2)submetacentric
3) acrocentric
4)teleocentric
There are 22 pairs of chromosomes in both male and female in which all the 21 pairs are similar in both and 22 nd pair in man is different. These are special types of materials when they got transmitted to a progeny then only half get transferred from male and half from females that's why the no is maintained.

Answer 2

human has two cells the normal cells have 48 chromosomes and sex cells have 24 chromosomes so we get 24+24=48 chromosomes from our mother and father.
chromosomes are the unit of inheritance . they contain DNA .
a pair of chromosomes is = 2 chromosomes
so, we have 24 pairs of chromosomes