A punnet square is a tabular chart used in genetics to display the genotypic composition of the offsprings of two parents. To construct a punnet square, the alleles of the gametes produced by the parents is required.
The gametes produced by each parent via meiosis are placed along the vertical and horizontal sides of the punnet square. For example, if a cross occurs between two parents with the following genotype: AaBb and AAbb. The parents will produce the following gametes:
AaBb - AB, Ab, aB, ab
AAbb - Ab, Ab, Ab, Ab
These gametes produces by each parent will be placed along the sides (vertical and horizontal) of a punnet square to determine the genotype of the offsprings that will be produced.
Mantle plumes that form hotspots are thought to be relatively stationary whereas the overlying tectonic plates typically are not. Thus, as a plate moves over the location of a plume eruption, it carries successively older volcanoes with it.
