Final answer:
Inheritance in pea plants follows Mendelian genetics, with dominant and recessive alleles determining traits such as plant height. A heterozygous tall pea plant crossed with another exhibits a 3:1 tall-to-short phenotypic ratio and a 1:2:1 genotypic ratio. Crosses with a dwarf plant result in a 1:1 ratio for both phenotypes and genotypes.
Step-by-step explanation:
In pea plants, the characteristic of height is determined by genes where tall is the dominant trait (T) over short (t). A pea plant that is homozygous dominant (TT) for the tall trait will be tall, just like a plant that is heterozygous (Tt). However, a plant that is homozygous recessive (tt) will display the short phenotype.
When a heterozygous tall pea plant (Tt) is crossed with another heterozygous tall pea plant (Tt), a Punnett square predicts the genotypic ratio of 1:2:1 (TT:Tt:tt) and a phenotypic ratio of 3:1 (tall:short). In contrast, crossing a dwarf pea plant (homozygous recessive, tt) with a heterozygous tall pea plant (Tt) yields a 1:1 genotypic and phenotypic ratio (Tt:tt and tall:short).
Mendelian genetics and the random segregation of alleles during gamete formation explain these ratios. This discovery was one of Mendel's crucial insights, deduced from extensive experiments with pea plants, including observing traits such as flower color and pea texture.