2. I.Genetics A. The work of Gregor Mendel 1. Monohybrid crosses 2. Dominant and recessive alleles 3. Law of Segregation B. Mendel and meiosis

6. Who was this Mendel and what the heck is he doing in a monastery? born in 1822 trained himself to be a naturalist early in life worked as a substitute science teacher failed the qualifying exams to be a regular high school teacher! joined a monastery in Brunn, Austria sent to Vienna U. to study science and math

8. Mendel’s first published work: "Versuche über Pflanzen-Hybriden“ or Experiments in Plant Hybridization was a landmark in clarity and insight! Trained as a mathematician and a biologist, he figured out the laws of inheritance… mathematically!! MendelWeb

9. The work of Gregor Mendel …he called them his children! worked with pea plants… Why pea plants??? There was a long-standing tradition of breeding pea plants at the monastery where Mendel lived and worked

10. So…they were readily available and they come in lots of varieties! …there were plants with different flower colors, seed color, flower position etc..

11. ‘Brother Greg... We grow tired of peas again!!!’

12. And best of all… Pea plants flowers can reproduce by themselves This allowed Mendel to see if strains were true breeding and to produce hybrids

13. How Mendel made hybrids… He’d then tie little bags around the flowers to prevent contact with stray pollen.

14. Mendel’s hybridization experiments… Monohybrid crosses: Parental Generation True-breeding purple flower x True-breeding white flower F 1 generation All purple flowers (the hybrids) F 2 generation Allowed F 1 offspring to self-fertilize 705 purple 224 white

16. The results of Mendel’s monohybrid crosses led him to propose… 1.All organisms contain two “units of heredity” for each trait (alleles). 2.Dominant and recessive alleles… …and organisms can have any combination of the two alleles (2 dominants, 2 recessives or a mixture 1 dominant and 1 recessive). 3.The Law of Segregation – during gamete formation, alleles separate randomly into separate gametes.

17. A bit of genetic jargon… phenotype vs. genotype What the organism looks like What alleles the organism has - its genetic makeup

18. More jargon… homozygous vs. heterozygous 2 of the same alleles: PP or pp 2 different alleles: Pp P p

19. A Punnett square

20. A Punnett square… Gametes from one parent P p Gametes from other parent P p PP purple PpPp PpPp pp purple white Ratio: 3:1 or ¾ purple, ¼ white

22. Let’s relate Mendel’s findings to what we now know about gamete formation True-breeding purple flower x True-breeding white flower PP p PPP p pppp all purple P P p

23. F 1 generation purple hybrid x purple hybrid P p P p P P P P pp pp PP pp PP (purple)Pp (purple)Pp - purplepp - white F2F2

24. Join to your partner and together, work on the following… Determine the phenotypic and genotypic ratios for each of the following monohybrid crosses. Genotypic ratio Phenotypic ratio 0:1:0 (hd:h:hr)1:0 (dom:rec) or all dominant AA x aa 0:1:1 (hd:h:hr)1:1 (dom:rec)aa x Aa 1:1:0 (hd:h:hr)1:0 (dom:rec) or all dominant AA x Aa 1:2:1 (hd:h:hr)3:1 (dom:rec)Aa x Aa hd = homozygous dominant; h = heterozygous; hr = homozygous recessive

25. SO, NOW IT’S YOUR TURN TO WORK ALONE http://www.mendel-museum.com/eng/1online/experiment.htm Click on the site below