We can now begin to define a series of important concepts that you should know about genetics.
Genes occur in pairs along chromosomes.
It is important to recognize that you possess genes in pairs. This is precisely what Gregor Mendel saw when he worked with peas. The following illustrates this point for a gene that governs the ability to roll your tongue. 20 People with a heterozygous genotype have 40 gene loci and 20 R genes and 20 r genes.