Question

Polyploidy gives
a. Hybrid vigour
b. Improved varieties
c. Gigas effect
d. All of the above

Answer 1

Polyploid is a condition commonly seen in plants, especially in angiosperms, which are described as cells having multiple sets of chromosomes, and generally cells having a single set of chromosomes are called as haploid, and if the cells having 2 sets of chromosomes, then they are called as diploid cells. So if the cell has multiple sets of chromosomes, then those are called Ploidy.

Complete answer:
- Polyploidy has occurred in the evolution of plants and this process can begin if diploid gametes are formed.
- The polyploidy arises in two ways, they are, if gametes which are formed by the mitotic division instead of meiotic division.
- Generally, plants are not animals, where they form the germ cells from the somatic tissues, so if the chromosome content of a precursor somatic cell has accidentally doubled, where gametes contain diploid( 2n) chromosomes.
- The polyploidy can occur both naturally as well as in induced forms when coming to examples of natural plant tissues with polyploidy are given below.
- As endosperm (3n) develops in certain plants such as corns, kernels where It undergoes certain rounds of endoreplication which produces the nuclei that are range as high as 6n, this gives the cells the appearance of giants, and the effect is called as gigas effect.
- When rhizobia infect the roots of their legume host, they induce the Infected cells to undergo endoreplication which produces the cells that are having the ploidy of 128n.
- The method of polyploidy can also be induced in laboratories and the occurrence of polyploidy in animals is rare.

Hence, the correct answer is option (C).

Note: In laboratory methods, they introduce certain drugs to the plants, where during mitotic cell division, they disrupt the formation of microtubules, which interrupt the spindle formation, so the division does not take place which results in the formation of diploid gametes.