Question

How do you write the heterozygous dominant genotype?

Answer 1

Genotype refers to genetic characters that are inherited in an organism from the parents and it forms the basic genetic makeup of an organism.

Complete answer:
For the representation of genes in genotype we can use different alphabets. Here in this question, we will consider the genotype of a pea plant which was considered by Mendel during his experiment.
Suppose we are using 'T' to represent the allele that is responsible for the tallness of the pea plant then we must use 't' to represent the allele responsible for dwarfness of the pea plant.
Here both T and t represent various forms that are tallness and dwarfness of a similar character that is the height of the pea plant and hence T and t forms alleles of a similar gene.

Now the possible pair of alleles using T and t are TT, tt, and Tt. If the pair contains alleles that are identical to each other then the pair is known as Homozygous whereas when the pair contains alleles that are not identical to each other they are known as heterozygous.
In the pea plant, the tall plant is dominant and the dwarf plant is recessive. Hence TT is a homozygous tall plant, tt is a heterozygous dwarf plant but the Tt plant was heterozygous but the phenotype of this plant was similar to a homozygous tall plant. Hence Tt is a heterozygous tall plant.
Hence heterozygous dominant genotype is written as Tt.

Note: Here we have not used D for dwarfness just because we considered T for tallness because it leads to confusion whether T and D are alleles of different genes or not. Hence the easiest method to avoid this confusion is to use the uppercase and lowercase of the same alphabet to represent alleles belonging to the same gene and using different alphabets to represent different genes.