Question

How do polyploidy individuals arise?

Answer 1

A polyploid is simply an organism that contains more than the usual two sets of chromosomes. For animals, this is a fairly rare occurrence. In plants, however, this is much more common and has played an important role in plant evolution.

Polyploidy may occur due to abnormal cell division, either during mitosis, or commonly during metaphase I in meiosis. Polyploidy can naturally arise in a number of different ways. In some cases a somatic (non-reproductive) mutation can occur, due to a disruption in mitosis, resulting in chromosome doubling in a meristematic cell(s) that will subsequently produce a polyploid shoot. These mutations or sports are often evident on a tree by their enlarged "gigas" condition. Polyploids can also result from the union of unreduced gametes - eggs and sperm that have not undergone normal meiosis and still have a 2n constitution.