Have you been over to Google today? If so, then you may have noticed their very neat "doodle" of peas. This Google doodle is honoring Gregor Mendel's 189th birthday. Happy Birthday Gregor!
Any genetics course starts with the basics: Peas. For thousands of years farmers and herders have been selectively breeding or crossbreeding their plants and animals to favor certain desirable traits. They knew that they could breed one animal to another and roughly what to expect the offspring to look like. What they didn't know were the mechanisms behind inheritance.
First, he chose the common pea plant (Pisum sativum) and identified various traits that he wanted to study: Plant height/stem length (long or short), pod shape (inflated or constricted), pod color (yellow or green), seed shape (round or wrinkled), seed color (yellow or green), flower position (axial or terminal), and flower color (purple or white). The beauty of the experiment is its simplicity. He chose an organism that was easy to rear, has male and female reproductive structures, can self-pollinate or cross-pollinate, and that has simple traits that can be categorized and quantified (notice how there are only 2 types of each trait?). From this experiment he developed his "First Law," the Law of Segregation. This law states that every individual has an allelic pair (pair of genes) for any particular trait and that during gamete formation each parent randomly passes on one of these genes to their offspring. Out of this passed on pair, the dominant gene will determine the expression of the trait. Up until this point Mendel has been following the expression of only one gene. Next he performed crosses where he followed the segregation of two genes. For example, both seed shape and seed color. These experiments were the basis for his "Second Law," the Law of Independent Assortment. This law states that separate alleles for separate traits are passed on independently of one another from the parents to the offspring. Simply, that the inheritance of one trait does not preclude or facilitate the inheritance of any other trait.
Obviously, we have expanded on Mendel's discoveries since then, but his concepts/laws still hold and are taught as the foundation of modern genetics. They are the basis for all those punnett squares you had to draw in high school biology class. In fact, even much of his terminology (dominant, recessive, allele, etc.) is still used today. That is amazing for a guy who never enjoyed recognition in his lifetime, his paper wasn't rediscovered until three decades later in 1900. Over the next hundred years or so scientists expanded on his ideas, added variations to his laws, and found and explored DNA itself.
If you aren't a scientist, or even if you are and need a good little refresher, I urge you to look back on Mendel's experiments. Especially since I only barely outlined his experiments. Here are some good places to start:
The Mendelian Genetics page from Intermediate Genetics at NDSU
Polomar College's Mendel's Genetics page
Deciphering the Genetic Code from the NIH (good for post-Mendel discoveries too)
Mendel's Profile from the Horticulture & Crop Science Department at The Ohio State University
You can read Mendel's original 1854 paper HERE
And some write-ups about Google's Mendel doodle from some popular news outlets:
"Google Doodle Honors Gregor Mendel, 'Father of Genetics'" from PC Magazine
"Google pays tribute to the father of genetics" from USA Today
"Google Doodle celebrates “father of genetics” Gregor Mendel’s 189th birthday" from Geek.com
And just for fun...