1. MENDEL’S WORK Key Concepts What were the results of Mendel’s experiments or crosses? What controls the inheritance of traits in organisms?

2. Key Terms  Heredity  Trait  Genetics  Fertilization  Purebred  Gene  Alleles  Dominant allele  Recessive allele  hybrid

3. Mendel’s Work  Mendel experimented with thousands of Pea plants looking at their different traits to understand the process of heredity. His discoveries form the foundation of genetics.  Heredity –the passing of physical characteristics from parents to offspring  Trait- each different form of a characteristic  Genetics – the study of heredity

4. Mendel’s Experiments  Flowering Plant anatomy  Pistil – produces the female sex cells or eggs  Stamens – produce pollen which contains the male sec cells or sperm  Fertilization is when the egg and sperm join forming a new organism  In plants the pollen must reach the pistil for fertilization to occur. This is called pollination

5. Pollination  Pea plants usually self- pollinate. The pollen from their stamens lands of the same plants pistils.  Mendel developed a method to cross-pollinate pea plants. He took pollen from one pea plant and brushed it onto the pistil of another.

6. Crossing Pea Plants  Mendel crossed plants with contrasting traits  Ex. Tall plants with short plants  Started with purebred plants – a purebred organism is one who is the offspring of many generations of that have the same trait

7. The F 1 Offspring  Mendel crossed purebred tall with purebred short Parental (P) generation  Tall x short  Offspring from the cross are called F 1 (filial)  All F 1 offspring were tall

8. F 2 offspring  When F 1 were full grown, Mendel allowed them to self-pollinate  F 2 were a mix of tall and short  ¾ were tall and ¼ were short

9. Experiments with OtherTraits  Mendel crossed pea plants with other contrasting traits such as seed shape, seed color, seed coat color, etc.  In all crosses the F1 generation had only 1 form of the trait  In the F2 generation the “lost” form reappeared in ¼ of the plants.

10. Dominant and Recessive Alleles  Mendel’s Conclusion  factors control the inheritance of traits in peas.  They exist in pairs  The female parent contributes one factor and the male parent contributes the other factor  One factor in a pair can mask or hide the other factor

11. Genes and Alleles  Genes – factors that control a trait  Alleles – different forms of a gene  An organisms traits are controlled by the alleles it inherits from its parents.  Some alleles are dominant, while others are recessive  Dominant allele – trait always shows  Recessive allele –trait is hidden whenever dominant allele is present

12. Alleles in Mendel’s Crosses  Stem Height Cross  P generation tall tall x short short  F1 generation all were tall short- Look tall  F2 generation ¼ tall tall - look tall ¼ tall short + ¼ short tall – look tall ¼ short short – look short

13. Symbols for alleles  Letters are used to represent alleles  Capital letters are used for dominant alleles  Lowercase letters are used for recessive alleles  Purebred tall = TT  Purebred short = tt  Hybrid (one of each) =Tt

14. Significance of Mendel’s Contribution  Before Mendel most people thought that the traits of an individual were a blend of their 2 parents.  If they blended the Tt plants should be medium height  Mendel found out that traits are determined by individual alleles some of which are dominant and some recessive.  Recessive traits may seem to disappear in the offspring only to reappear in the next generation  Mendel’s work was not recognized during his lifetime, but was rediscovered in 1900. He is now considered the Father of Genetics.

15. Sources  http://kentsimmons.uwinnipeg.ca/cm1504/mendel.htm http://kentsimmons.uwinnipeg.ca/cm1504/mendel.htm  http://www.exploringnature.org/db/detail.php?dbID=45&detID=2290 http://www.exploringnature.org/db/detail.php?dbID=45&detID=2290  http://ncse.com/files/images/pea_plant.preview.jpg http://ncse.com/files/images/pea_plant.preview.jpg  http://library.thinkquest.org/28751/review/plants/6.html http://library.thinkquest.org/28751/review/plants/6.html  http://www.cactus-art.biz/note- book/Dictionary/Dictionary_C/dictionary_cross_pollination.htm http://www.cactus-art.biz/note- book/Dictionary/Dictionary_C/dictionary_cross_pollination.htm  http://academic.kellogg.edu/herbrandsonc/bio111/genetics.htm http://academic.kellogg.edu/herbrandsonc/bio111/genetics.htm  http://www.bioinformatics.nl/webportal/background/mendelinfo.html http://www.bioinformatics.nl/webportal/background/mendelinfo.html  http://www.absoluteastronomy.com/topics/Experiments_on_Plant_Hybridization http://www.absoluteastronomy.com/topics/Experiments_on_Plant_Hybridization  http://www.csulb.edu/~kmacd/361-6-Ch2.htm http://www.csulb.edu/~kmacd/361-6-Ch2.htm  http://library.thinkquest.org/17109/tutorial.htm http://library.thinkquest.org/17109/tutorial.htm  http://www.learner.org/interactives/dna/genetics3.html http://www.learner.org/interactives/dna/genetics3.html  http://cynthialeitichsmith.blogspot.com/2010/06/guest-post-sharron-l-mcelmeel- on.html http://cynthialeitichsmith.blogspot.com/2010/06/guest-post-sharron-l-mcelmeel- on.html