BOTANY Higher Secondary Second Year - Textbooks Online

Aneuploidy
Variation that involves one or two chromosomes within the diploid
set of an organism results in aneuploidy. It is of two types – hypoploidy
and hyperploidy.
Hypoploidy
Decrease in one or two chromosomes from the diploid set is described
as hypoploidy. There are two types of hypoploidy – monosomy and
nullisomy. Monosomy is due to loss of a chromosome from the diploid
set i.e. 2n – 1. Nullisomy is the condition in which a pair of homologous
chromosomes is lost from the diploid set i.e. 2n – 2.
Hyperploidy
Addition of one or two chromosomes to the diploid set of chromosome
results in hyperploidy. There are two types of hyperploidy – trisomy and
tetrasomy. Trisomy results due to the addition of one chromosome to diploid
set of chromosomes. It is represented by 2n + 1. Trisomics are observed
in Datura stramonium. Tetrasomy results due to the addition of two
chromosomes to diploid set of chromosome. It is represented by 2n+2.
Significance of ploidy
Polyploidy plays an important role in plant breeding and horticulture.
Polyploidy has more vigorous effect than the diploids and results in
the production of large sized flowers and fruits. Hence, it has
economical significance.
It plays significant role in the evolution of new species.
Polyploidy results in the changes in the season of flowering and
fruiting.
Polyploids are vigorous invaders of new habitats.
It leads to the formation of new varieties which show high resistance
to disease and increase in yield.
Tetraploid cabbages and tomatoes contain more ascorbic acid whereas
tetraploid corn contains more vitamin A.
Both euploidy and aneuploidy in man cause congenital diseases.
Polyploidy varieties like apple, pear, grape and watermelons are
cultivated because of their large size.
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