Biology (A)

Traits, Genes, and Alleles

Interpreting Mendel’s discoveries through the eye of modern genetics, we now know that Mendel’s hereditary factors are made up of DNA. Recall that our DNA is wound into chromosomes. Each of our chromosomes contains a long chain of DNA that encodes hundreds, if not thousands, of genes. Each of these genes can have slightly different versions from individual to individual. These variants of genes are called alleles. For example, remember that for the height gene in pea plants there are two possible alleles, the dominant allele for tallness (T) and the recessive allele for shortness (t).