Gregor Mendel The Ferdinand Magellan of Genetics
Gregor Mendel was an Austrian monk who discovered the basic tenets of genetics through breeding experiments with peas.
They were all tall! Why? • Some genes (like the one for plant height) have two contrasting forms, called alleles. • Mendel determined that the allele for shortness was completely masked by the presence of the allele for tallness. • In other words, Tallness (T) is dominant and shortness (t) is recessive.
He found this principle of dominance to be true for many other pea traits, too!
How did short plants reappear? • When sex cells (or gametes) form, alleles must separate (or segregate) from each other so that each sperm and each egg only has one allele. • When fertilization occurs, the alleles recombine randomly. • If two recessive alleles pair up, the recessive trait will now be shown!
Let’s act out Mendel’s crosses to see how this happens…Who wants to be a gamete?
TWO TASKS:1. Grab a laptop and complete the WebLab in today’s daily agenda (accessible from Moodle)2. Upon completion of the WebLab, start your homework assignment, which is due tomorrow.