1. MENDELS GENETICSBy: NOMSA REASON TOLIBADI

2. MENDELS GENETICSThe first recorded scientific study of how traits pass from one generation to the next was done by Gregor Mendel, a monk! 1. In 1856, he began experimenting with garden peas. 3. MENDELS GENETICS 3. He believed he could predict the kinds of flowersand fruits a plant would produce. a. To do this he believed that something had to be known about the parents of the plants.4. Each different form of a characteristic, such as astem height, is called a TRAIT. 5. Today, Mendels discoveries form the foundation of Genetics. a. Father of Genetics 4. Mendels Experiments 1. Fertilization occurs when egg and sperm join. a. Before this can happen in pea plants, pollen mustreach the pistil of the flower. This process is called pollination.2. Mendel developed a method by which he cross pollinated, or crossed pea plants. 5. Why the Garden Pea? Many varieties 32 to start used 7 More than one form of the same trait Small, easy to grow, matures quickly, large numbers of offspring Ability to cross-pollinate and self-pollinate 6. Crossing Pea Plants 1. An organism that always produces the same traitsin its offspring is called a PUREBRED. a. Example: PUREBRED short pea plants always come from short parent plants.b. Tall plants that always produce tall plants are considered PUREBRED tall plants. 7. Crossing Pea Plants 2. In one experiment, Mendel crossed purebred tall plants with purebred short plants. a. Scientists call the parent plants the parentalgeneration or the P generation b. The offspring from this cross are the first fillial generation or the F1 generation. i. Fillial comes from the word fillia: the Latin word for daughter c. All of the offspring from this cross were TALL. 8. Crossing Pea Plants 3. When the plants in the F1 generation were full grown, Mendel allowed them to self pollinate.a. Some of the plants in the F2 generation were a mix of tall and short plants.i. were tall ii. were short. 9. Genetics Dominant and Recessive Traits 1. Genes are factors that control traits. a. Genes are made up of DNAb. Genes are found on chromosomes. 10. Explain the principle of dominance and recessive 11. Dominant and Recessive Trait: 1. The different forms a gene may have for a trait are its alleles.2. Each new organism inherits two alleles from its parents. a. One from the egg (mother) and the other from the sperm (father). b. A pea plant may inherit two alleles for tall stems, two alleles for short stems, or one of each. 12. Dominant and Recessive Traits 3. An organisms traits are controlled by the alleles it inherits from its parents.a. Dominant Allele is one whose trait always shows up in the organism when the allele is present.b. Recessive Allele is hidden whenever the dominant allele is present. A trait controlled by a recessive allele will only show up if the does not have the dominant allele.organism 13. Mendels proposed Theory Parents pass factors(genes) to their offspring that produce traits. Two alleles for each trait heterozygous (Tt) or homozygous (TT, tt) Phenotype = physical appearance Genotype = set of alleles Dominant is expressed over recessive 14. Alleles and AppearanceTTTallttTtDwarfTall 15. Mendels Laws: Law of Segregation Mendel found that there were three principles ofinheritance resulting from the study of pea plants for seven characteristics. In so doing, he found that traits of the parent generation do not blend in those of their offspring. Rather, one gene for each trait is segregated from other genes for other traits. Segregation: Separation of alleles in the formation of gametes (sex cells) 16. Mendels Law: Law of Independent Assortment differing traits are: inherited independently of each other (genes on separate chromosomes) For example whether a pea plant flower is violet or white is separated from smooth or wrinkled peas In other words, a white flowering plant can yield either a wrinkled or a smooth pea; so can a violet flowering plant So flower color is independent from smoothness of peas The PHC assortments in the Punnett Squares are another example of this law. 17. Interpreting Mendels Model Capital letters= dominant alleles Lower case letters = recessive alleles Two alleles for each traitHomozygous dominant = DD Heterozygous dominant = Dd (hybrid) Homozygous recessive - dd 18. Summarize Mendels conclusions about inheritance 19. Summary Trait Dominant and Recessive Traits in Pea Plants are shown in the table to the right.If the dominant allele is present it will mask the recessive allele.Example: If a pea plant has both purple and white flower alleles the purple allele will be the one that is visible to you.DominantRecessive 20. The Monohybrid Cross: Provide information about one pair of contrasting traits. X P (parents)F1 (first filial generation)F2 (second filial generation)Filial = son / daughterX 21. The Monohybrid Cross Parentsxbb bGametes allxbbSecond generation (F2)b bbAll offspring (F1)Gametes allbbbbb bbb 22. The Monohybrid Cross Can also be shown in a punnet square: o A handy tool to use to predict results in Mendelian Genetics is the Punnett Square.X BBo Punnett Square is a chart that shows all the possible combinations of alleles that can result from a genetic cross.bb BBbBbBbbBbBbAll offspring: black 23. Probability and Heredity a. Phenotype 1.An organisms phenotype is its physical appearance, or its visible traits.2.Phenotypic Ratioa.The ratio of phenotypes found in the Punnett Square.b.Pea plants can have one of two different phenotypes for stem height-Short or Tall.b. Genotype 1.An organisms genotype is its genetic makeup, or allele combinations.2.Although all of the tall plants have the same phenotype, they can have two different genotypes-TT or Tta.A Genotypic Ratio is the ratio of genotypes found in a Punnett Square. 24. 5 Factors that Influence Heredity #1 Incomplete Dominance A trait is displayed that is intermediate between two parents. Flower color in snapdragons Red + White = Pink 25. #2 Codominance Two dominant alleles areexpressed simultaneously Different from incomplete dominance because both traits are displayed Example) roan coat in horses is a result of a cross between a homozygous red and homozygous white horseresulting in a horse with a coat of red and white hair. 26. #3 Multiple Alleles Genes with more than one allele Example) three alleles can determine blood type (A, B, and O) A and B are dominant over O Neither A nor B are dominant over each other When A and B are presentthey are codominant 27. #4 Continuous Variation Several genes influence a trait Examples) height and weight A variety of phenotypes exist from one extreme to another 28. #5 Environmental Influences Phenotypes being influenced by the environment Example) the coat color of the arctic fox in winter 29. Conclusion Genes are ultimately responsible for our traits Cells are maintained by cell division called mitosis Our traits are passed down from one generation to the next by meiosis Through meiosis, we can predict what traits will be passed down and in what proportion. 30. Credits: Genetics and inheritance With consent from Mrs Janice Williamson by Danelle_ Oosthuizen, 9 months ago in Technology. Genetics section 1 notes by joelmotuk, 3 years ago in Education. Mendel genetics by candeehovis, 3 years ago in Technology. Mendelian genetics by mcnewbold on Jan 18, 2012.