However, a hybrid (heterozygous) tall plant has both a tall and short allele in each body cell. During meiosis, the alleles separate and the sex cells receive either a tall or short gene. (We will use egg cells as an example.)
Parent Plant
Body Cells
Possible Gametes - Egg Cells

Heterozygous Tall

Mendel was the first scientist to predict the results of genetic crosses. Scientists now use a chart called "Punnett squares" to show all of the possible outcomes of a genetic cross. On the outside of the square, the genotypes of both parents are listed. This is equivalent to the two genes found in each body cell. Above each square, the possible gamete alleles donated by each parent are listed. Inside each square the combinations of alleles created by the union of egg and sperm are listed. These alleles represent the possible offspring genotypes.

Consider Mendel's first experiment. He crossed a purebred (homozygous)tall plant with a purebred (homozygous) short plant. The Punnett square would be set up as follows. All offspring will be tall. Click inside each cell to see the resulting genotypes of the offspring.

Male Parent Body Cell
Possible Sperm

Possible Sperm

Female
Parent
Cell

Possible egg
Possible egg