What is the inheritance pattern demonstrated when a heterozygous plant crosses with a homozygous recessive plant, resulting in about half of the offspring showing the dominant trait?

• A. Mendelian dominant-recessive inheritance
• B. Incomplete dominance
• C. Codominance
• D. Polygenic inheritance

Answer: (A)

This shows simple Mendelian dominant-recessive inheritance with complete dominance. When a heterozygous plant (one dominant allele and one recessive allele) crosses with a homozygous recessive plant, each offspring gets one allele from each parent. The heterozygous parent can pass either the dominant or the recessive allele, while the recessive parent can only pass the recessive allele. This yields offspring genotypes Aa and aa in a 1:1 ratio, and the Aa plants display the dominant trait while the aa plants display the recessive trait. So about half of the offspring show the dominant trait and half show the recessive trait, which is characteristic of classic dominant-recessive inheritance.

Incompletely dominant cases would show an intermediate phenotype in heterozygotes, not a clear dominant trait in half the offspring. Codominance would have heterozygotes expressing both traits simultaneously. Polygenic inheritance would produce a continuous range of phenotypes rather than two distinct groups.