Question

In a guava fruit, there were 300 seeds. How many meiotic divisions must have been involved in the development of 300 seeds?
(A) 75
(B) 300
(C) 375
(D) 450

Answer 1

Hint:- Guava is a tropical fruit belonging to angiosperms, which are a group of flowering plants. These flowering plants produce seeds through sexual reproduction involving both the male and female gametes.

Complete Answer:- Guava reproduces both sexually and asexually. It can be subjected to vegetative propagation through grafting, budding, air layering etc. But in sexual reproduction, both the male gamete (pollen grains) and female gamete (megaspore) are involved for which pollination plays a major role. The cells of an organism divide through either mitosis (in somatic cells) or meiosis (in germ cells). The gametes being germ cells undergo meiosis producing sperms or eggs. Meiosis takes two rounds of division to produce the cells, as follows,
In the first division, the chromosomes from the maternal and paternal genetic material are crossed over producing new unique combinations of chromosomes in each gamete.
In the second division, sister chromatids are formed to produce haploid cells. This division is essential for spermatogenesis and oogenesis.
Though the division is the same for both the gametes, equal numbers of cells are not produced at the end.
In megasporogenesis, four megaspores are produced through meiosis in the ovule. However, only one megaspore remains functional at maturity, which eventually produces one egg cell.
The microspores are produced from microsporangium of the anther. After meiosis, the microsporangia produces four haploid cells, which becomes pollen grains after mitosis.
Now let us find the number of meiotic divisions involved to produce 300 seeds. A seed is formed from the fertilisation of a pollen and an egg cell, which then becomes a zygote. So 300 pollen and 300 egg cells produce 300 seeds. If one meiotic division produces one egg cell, it would have taken 300 meiotic divisions to produce 300 eggs. Similarly, four pollens can be produced through one meiotic division in male gametes. So, 75 meiotic divisions give 300 pollen.

Thus, (C) 375 meiotic divisions are involved in producing 300 seeds in guava

Note:- As meiotic division happens in sexual reproduction, the offspring produced have diverse traits because of chromosomal crossing over. This is not possible through vegetative propagation, as the offspring will be a clone of their parent plant.