The document discusses Gregor Mendel's pioneering work in genetics using pea plants. It explains that Mendel used Punnett squares to predict the expected ratios of traits being passed on from parents to offspring. While Punnett squares can predict ratios, the actual observed results do not always match expectations if one parent is heterozygous for a trait. Mendel's careful experiments demonstrated that traits can be dominant or recessive and are passed on through discrete units (now known as genes), fundamentally shaping the field of genetics.

1. 26:2 Expected Results and Observed Results Objectives: Discuss the purpose of the Punnett square Compare expected results and observed results Explain the importance of Gregor Mendel’s work

2. The Punnett square The Punnett square is a way to show which genes can combine when a sperm and egg joins. Letters are used in place of genes A capital letter is used for the dominant gene A lower case letter is used for the recessive gene

3. Pure recessive color Lower case letters Capital letters are dominant and the trait will show Heterozygous color One capital letter, one lower case letter

4. Expected Results Using the Punnett square you are able to predict traits in offspring. The ratio is 1:4 that a dominate trait will show.

5. Observed Results You can not always see the expected results using a Punnett square. One parent can have a heterozygous trait while the other parent has a pure recessive trait .

6. If that occurs then there is a 50% chance that the trait will show. http://www.google.com/imgres?q=punnett+square+examples&hl=en&biw=1270&bih=683&gbv=2&tbm=isch&tbnid=6eR6nC9th1Q6QM:&imgrefurl=http://www.exploringnature.org/db/detail.php%3FdbID%3D22%26detID%3D2290&docid=4iunWTrHoOHeVM&imgurl=http://www.exploringnature.org/graphics/anatomy/Punnetts_square.jpg&w=538&h=720&ei=HCEvT4KOFJHpggfMs8TUDw&zoom=1&iact=hc&vpx=184&vpy=125&dur=3414&hovh=260&hovw=194&tx=87&ty=159&sig=110912335990059377268&page=1&tbnh=157&tbnw=122&start=0&ndsp=18&ved=1t:429,r:0,s:0

7. Mendel’s work Gregor Mendel was an Australian monk in 1805. He notices certain traits in garden pea plants Using the scientific method he experimented to find out which traits were recessive and which were dominant in pea plants.

8. One trait he noticed was height . He observed that when a tall plant was mated with a short plant all of the offspring was always tall. He then took the tall offspring and mated them and found that 3/4 of the plants produced were tall and 1/4 were short .

10. Mendel concluded that some traits were present in the tall plants, but were not seen His experiments explained the basic law of genetics