Which of the following causes polyploidy?
(a) Polyspermy
(b) Diploid Gametes
(c) Double Fertilisation
(d) All of these
Explain your answer with appropriate reasons.
Answers
Answer:
d) All of these
Explanation:
⮕ Polyploidy is the phenomenon that occurs due to the failure of cytokinesis after the telophase stage of cell division which results in an increase in the whole set of chromosomes in the organism. Here the organisms have more than two sets of homologous chromosomes.
⮕ This is usually common in plants and rarely seen in humans. Such individuals are usually sterile.
⮕ The increase in the chromosome number involving the same set of chromosomes within a species is called autopolyploidy and sets from different species is called allopolyploidy.
a) Polyspermy:
This is usually seen in angiosperms. It occurs when a diploid cell fuses with a haploid cell resulting in a triploid (3x) zygote. (Triploidy) The triploid zygote by mitotic division divides into two celled embryos and later develop into a triploid plant. This occurs due to the failure of one meotic division of the gametes.
b) Diploid gamete:
Two diploid gametes fuse together to form a tetraploid (4x) zygote. This happens during meosis in which there is a failure of segregation of the chromosomes and there is no reduction in the chromosomal number. A tetraploid and diploid gamete fuse together to form a triploid gamete.
c) Double Fertilization:
In flowering plants, one of the male gamete fuse with the egg cell to form a diploid zygote. (syngamy) The other male gamete fuses with the two polar nuclei to produce a triploid (3x) PEN (Primary endosperm nucleus) called as triple fusion which later develops into the endosperm and provides nutrition to the developing embryo.
Question:-
Which of the following causes polyploidy?
- (a) Polyspermy
- (b) Diploid Gametes
- (c) Double Fertilisation
- (d) All of these
Answer:-
- All of the above