A comparison of a trait (height) that shows discontinuous and continuous phenotypes in different pla

A comparison of a trait (height) that shows discontinuous and continuous phenotypes in different plants. (a) Histograms show the percentage of plants with different heights in crosses between tall and dwarf strains of the pea plant. The F1 generation has the tall phenotype, and the F2 has two distinct phenotypic classes: 75% of the offspring are tall, and 25% are dwarf. (b) Histograms show the percentage of plants with different heights in crosses between tall and dwarf strains of tobacco plants carried to the F2 generation. The F1 generation is intermediate to the parents in height, and the F2 shows a range of phenotypes from dwarf to tall. Most plants have a height intermediate to those of the P1 generation. The differences between the pea plants and tobacco plants are explained by the fact that height in tobacco plants is controlled by two or more gene pairs, whereas height in peas is controlled by a single gene.