During the meiosis process where the fusion of the two chromosomes takes place from the father and the mother, there should be proper fusion. If the fusion is not proper and if the cells are still apart then this would result in multiple chromosomes nucleus called as the Polyploid. This is a type of anomaly that occurs during the meiosis process. Formation of Polyploid cells could happen in two ways. One is autopolyploid and the other is the allopolyploid.
An autopolyploid nucleus is a type of Polyploid nucleus which, is formed when the single cell has diploid set of chromosomes both from the same parent. This means that the chromosomes are homologous rather than fusion from different species during reproduction.
Cells containing this set of nucleus do not undergo meiosis at all. The sole condition of meiosis is that they should have one-one cell, which are form two different parents. This condition should be satisfied during the Prophase I of the meiosis phase. Now, since the condition is not satisfied and there are two homologous cells the nucleus becomes an autopolyploid. Now when pairing occurs and there are more than two homologous cells, then there would be much more confusion in pairing them. This results in a Polyploid condition leading to anomaly in the meiosis.
The next type of nucleus is the allopolyploid nucleus. This happens when more than the required number of species contributes to the nucleus chromosomes. For example, we could consider the grain wheat. This wheat is a cross between three types of grasses. Since all the three types are contributing, they hold six set of chromosomes. Each set of chromosome has one homologous pair. This makes them perfect for a complete meiosis.
Initially, such allopolyploids are formed from different type organisms belonging to the same species. This occurred accidentally. However, as man researched to find the advantages for such accidental cross-fertilizations he started to use this method to perform asexual reproduction and to yield several varieties of crops and populate a species. By this way, we can avoid meiosis and getting an exception at this step. This ability of plants has proved that if meiosis is disabled in species then survival is still possible.