Gregor Mendel (1822-1884) Austrian monk Gardener, scientist, teacher, mathematician A truly brilliant man Father of genetics

Mendel’s experiments Studied pea plants and followed the traits passed from one generation to the next. Cross-pollinated by hand literally thousands of plants over many years. Closely studied traits such as seed color, seed shape, pod shape, pod color, flower color, etc…

When Mendel crossed various pea plants he discovered interesting, but predictable results, over and over again. What surprised him the most, was how a trait could “skip” a generation, as if it disappeared, only to reappear in the next generation. Here’s one example (next slide):

Mendel also noticed that certain traits appeared to be “stronger” than others. He called them dominant. The weaker trait he called recessive.

Mendel’s conclusions: Hereditary traits are passed from parents to their offspring during sexual reproduction. For each trait, there are two hereditary “factors” - one from the mother and one from the father. The two inherited factors may be alike (as in purebred), or different (as in hybrid). When they are different, only one will be visible. The visible factor is called dominant. The hidden factor is called recessive.

Modern terminology Alleles - what Mendel called “factors”. Different forms of a gene. One allele from each parent. Might be the same from each parent, or different. Genes often occur in pairs of alleles. Homozygous - what is often called “purebred” (same alleles from both parents). Heterozygous - what is often called “hybrid” (two unlike alleles from each parent).