what is polyploidy? and pleiotropy and polygenic ?

Polygenic trait:- Those traits that are produced by the combined effect of many genes are called as polygenic traits. It is controlled by more than one pair of non allelic genes & shows a different types of phenotypes. for example-  Skin colour of an organism is an example of a polygenic trait.

Pleiotropy:- When a genes shows a multiple phenotypic effect, it is known as pleiotropy and the gene is known as pleiotropic gene. For example- In garden pea, the gene which controls the flower colour also controls the colour of the seed coat &  the presence of  red spots in the leaf axils.

Polyploidy:- Polyploidy is condition where an extra set of chromosome apart from diploid (2n) is found for example 3n, 4n, 5n etc.