How can you establish whether an organism with a dominant phenotype for the gene under study

How can you establish whether an organism with a dominant phenotype for the gene under study is homozygous or heterozygous, what is the name of this type of crossing?

Analyzing crossing – crossing of the studied organism with an individual homozygous for a recessive trait. If a 1: 1 split of phenotypes is observed in the offspring, then the studied individual is heterozygous, if all offspring are the same in phenotype, it is homozygous.

R: Aa x aa – the investigated individual is heterozygous;

G: A, a x a;

F: Aa – 50% phenotype for the dominant;

aa – 50% recessive phenotype.

R: AA x aa – the examined individual is homozygous;

G: A x a;

F: Aa –100% phenotype by dominant.