Maize Chromosome Number

Ploidy of Maize

Maize has two sets of chromosomes in each of its cells, making it diploid. Ploidy is the term used to describe the number of sets of chromosomes in each cell of an entity.

Maize, also referred to as corn, belongs to the Genus Zea with species name Z. mays. This facultative short-day plant is diploid, having 20 chromosomes (2n=20, n=10) and is characterized by the presence of “chromosomal knobs” - extremely repetitive heterochromatic domains that leave dark stains.

The centromeres are composed of two types of structural components, which are only found in the centromeres: a short satellite DNA, large arrays of CentC, and a certain family of retrotransposons. Although the centromeres can occasionally shrink during division, they are still able to fulfill their purpose, even if they become smaller than a few hundred kilobases. The kinetochores contain RNA, which is derived from the centromeres.

Inheritance in Maize

Maize is diploid; each of the cells in them comprises two sets of chromosomes, one from each parent (wheat is polyploid). At the time of meiosis, cells undergo division forming gametes wherein cells have one set of chromosomes only to prepare for the process of fertilisation.

At the time of fertilisation, gametes from one parent unite with the gamete of the other parent, forming a new individual. Maize is an angiosperm; the section of the carpel that receives pollen is the stigma. The silk in maize is the stigma, and tassels pass the pollen. Each of the silks accepts one pollen grain, which then moves down the silk for fertilisation of the egg at its base.

A silk has one egg at its base that accepts one pollen grain; hence each of the kernels is, in reality, a distinct individual with its own set of genes.

Cross-pollination between different plants is less likely for maize, resulting in self-pollination and a loss of vigour known as inbreeding depression. However, when two different parents of maize cross-pollinate, the progeny are often bigger and healthier than either of the parents - a process known as heterosis or hybrid vigour.

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