In this chapter, we focused on the Mendelian postulates, probability, and pedigree analysis. We also considered some of the methods and reasoning by which these ideas, concepts, and techniques were developed. On the basis of these discussions, what answers would you propose to the following questions: How do we know whether an organism expressing a dominant trait is homozygous or heterozygous?

Key Concepts

Mendelian Genetics

Mendelian genetics is the study of how traits are inherited through generations, based on the principles established by Gregor Mendel. It includes concepts such as dominant and recessive alleles, where dominant traits are expressed in the phenotype even if only one copy of the allele is present. Understanding these principles is crucial for determining the genetic makeup of organisms exhibiting dominant traits.

Homozygosity vs. Heterozygosity

Homozygosity refers to having two identical alleles for a particular gene, while heterozygosity means having two different alleles. When an organism expresses a dominant trait, it could be either homozygous dominant (two dominant alleles) or heterozygous (one dominant and one recessive allele). Distinguishing between these two states is essential for predicting inheritance patterns in offspring.

Test Cross

A test cross is a breeding experiment used to determine the genotype of an organism expressing a dominant trait. By crossing the organism with a homozygous recessive individual, the offspring's phenotypes can reveal whether the dominant organism is homozygous or heterozygous. The ratio of dominant to recessive offspring provides insight into the genetic composition of the parent organism.