Height is indeed a genetically determined trait influenced by multiple genes. In this context, we often refer to dominant and recessive phenotypes. If tallness is considered the dominant phenotype, it means that individuals with at least one dominant allele will exhibit this trait.
Matthew is described as heterozygous, which means he has two different alleles for the height gene—one for tallness and one for shortness. In terms of genotype, we can denote the dominant allele for tallness as ‘T’ and the recessive allele for shortness as ‘t’. Therefore, as a heterozygous individual, Matthew’s genotype would be ‘Tt’. This means he carries one allele for tallness and one for shortness but will express the dominant trait of being tall.