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Genetics section 1 notes

  1. 1. Genetics: The Science of Heredity<br />12th Applied Science <br />SECTION 1: MENDEL’S WORK<br />By<br />
  2. 2. Gregor Mendel<br />The first recorded scientific study of how traits pass from one generation to the next was done by Gregor Mendel, a monk!<br />In 1856, he began experimenting with garden peas. <br />I. Introduction to Genetics<br />
  3. 3. I. Introduction to Genetics<br />He believed he could predict the kinds of flowers and fruits a plant would produce. <br />To do this he believed that something had to be known about the parents of the plants. <br />Each different form of a characteristic, such as a stem height, is called a TRAIT.<br />Today, Mendel’s discoveries form the foundation of Genetics. <br />Father of Genetics<br />
  4. 4. I. Introduction to Genetics<br />Mendel’s Experiments<br />Fertilization occurs when egg and sperm join. <br />Before this can happen in pea plants, pollen must reach the pistil of the flower. This process is called pollination. <br />Mendel developed a method by which he cross pollinated, or “crossed” pea plants. <br />
  5. 5. I. Introduction to Genetics<br />Crossing Pea Plants<br />An organism that always produces the same traits in its offspring is called a PUREBRED. <br />Example: PUREBRED short pea plants always come from short parent plants. <br />Tall plants that always produce tall plants are considered PUREBRED tall plants. <br />
  6. 6. I. Introduction to Genetics<br />Crossing Pea Plants<br />In one experiment, Mendel crossed purebred tall plants with purebred short plants. <br />Scientists call the parent plants the parental generation or the “P generation”<br />The offspring from this cross are the first fillial generation or the “F1 generation”.<br />Fillial comes from the word fillia: the Latin word for daughter<br />All of the offspring from this cross were TALL. <br />
  7. 7. I. Introduction to Genetics<br />Crossing Pea Plants<br />When the plants in the F1 generation were full grown, Mendel allowed them to self pollinate. <br />Some of the plants in the F2 generation were a mix of tall and short plants. <br />¾ were tall<br />¼ were short. <br />
  8. 8. I. Introduction to Genetics<br />
  9. 9. Dominant and Recessive Traits<br />Genes are factors that control traits. <br />Genes are made up of DNA<br />Genes are found on chromosomes. <br />I. Introduction to Genetics<br />
  10. 10. Dominant and Recessive Traits<br />The different forms a gene may have for a trait are its alleles. <br />Each new organism inherits two alleles from its parents. <br />One from the egg (mother) and the other from the sperm (father). <br />A pea plant may inherit two alleles for tall stems, two alleles for short stems, or one of each. <br />I. Introduction to Genetics<br />
  11. 11. Dominant and Recessive Traits<br />An organisms traits are controlled by the alleles it inherits from its parents. <br />Dominant Allele is one whose trait always shows up in the organism when the allele is present. <br />Recessive Allele is hidden whenever the dominant allele is present. <br />A trait controlled by a recessive allele will only show up if the organism does not have the dominant allele. <br />I. Introduction to Genetics<br />
  12. 12. Dominant and Recessive Traits in Pea Plants are shown in the table to the right. <br />If the dominant allele is present it will mask the recessive allele. <br />Example: If a pea plant has both purple and white flower alleles the purple allele will be the one that is visible to you. <br />I. Introduction to Genetics<br />
  13. 13. II. Probability and Heredity<br />Probability<br />Probability is the number that describes how likely it is that an event will occur. <br />Probability is different then the odds. <br />Probability = what you want / total chances<br />Odds= what you want: what you don’t want<br />
  14. 14. II. Probability and Heredity<br />Punnett Squares<br />A handy tool to use to predict results in Mendelian Genetics is the Punnett Square.<br />A Punnett Square is a chart that shows all the possible combinations of alleles that can result from a genetic cross. <br />Y= Yellow<br />y= Green<br />
  15. 15. II. Probability and Heredity<br />Punnett Squares<br />Dominant alleles are represented by capital letters. <br />Recessive alleles are represented by lower case letters. <br />An organism that has two identical alleles is called HOMOZYGOUS. <br />An organism that has two different alleles is called HETEROZYGOUS. <br />Y= Yellow<br />y= Green<br />Yy= Heterozygous<br />yy= Homozygous<br />
  16. 16. II. Probability and Heredity<br />Using a Punnett Square<br />Monohybrid Cross deals with only one trait. <br />Yellow pea plants being crossed with green pea plants. <br />Di-hybrid cross deals with two traits. <br />a. Tall Yellow Pea Plants crossed with Tall Green Pea Plants<br />
  17. 17. TtYy X TtyyTall Yellow Pea Plants X Tall Green Pea Plants<br />Plant one is Heterozygous Tall; Heterozygous Yellow. <br />Plant Two is Heterozygous tall green pea plants. <br />
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  19. 19. II. Probability and Heredity<br />Phenotype <br />An organisms phenotype is its physical appearance, or its visible traits. <br />Phenotypic Ratio<br />The ratio of phenotypes found in the Punnett Square. <br />Pea plants can have one of two different phenotypes for stem height-Short or Tall. <br />Genotype<br />An organisms genotype is its genetic makeup, or allele combinations. <br />Although all of the tall plants have the same phenotype, they can have two different genotypes-TT or Tt<br />A Genotypic Ratio is the ratio of genotypes found in a Punnett Square. <br />
  20. 20. Comparing Phenotype and Genotype<br />II. Probability and Heredity<br />
  21. 21. G. CoDominance<br />H. Incomplete Dominance<br />For some alleles, an inheritance pattern called co-dominance exists. <br />In co-dominance, the alleles are neither dominant nor recessive. <br />As a result, both alleles are expressed in the offspring. <br />When two traits are not completely dominant over each other. <br />This results in a blending of the two traits.<br />Example:<br />RR = Red Flowers<br />WW= White Flowers<br />RW = Pink flowers <br />II. Probability and Heredity<br />
  22. 22. Please Review the following videos on Blended Schools:<br />Mendelian Genetics- A Quick Tutorial<br />Incomplete and Codominance Review<br />End of Genetics Section I Notes!!<br />Complete the Punnett Square Packet!!<br />II. Probability and Heredity<br />
  23. 23. Punnett Square Packet Answers<br />