1. 1 Please pick up a copy of the notes. Please pick up a copy of the notes.

2. 2 Mendelian Genetics

3. 3 Gregor Mendel “the Father of Genetics”

4. 4 Gregor Mendel (1822-1884)

5. 5 Gregor Johann Mendel  Austrian monk  Studied the inheritance of traits in pea plants  Developed the laws of inheritance  Mendel's work was not recognized until the turn of the 20th century

6. 6 Gregor Johann Mendel  Between 1856 and 1863, Mendel cultivated and tested some 28,000 pea plants  He found that the plants' offspring retained traits of the parents  Called the “Father of Genetics"

7. 7 Site of Gregor Mendel’s experimental garden.

8. 8  Mendel stated that physical traits are inherited as “particles”  Mendel did not know that the “particles” were actually Chromosomes & DNA Particulate Inheritance

9. 9 Mendel’s Pea Plant Experiments

10. 10 Why peas, Pisum sativum?  Can be grown in a small area  Produce lots of offspring  Produce pure plants when allowed to self- pollinate several generations  Can be artificially cross-pollinated

11. 11 Reproduction in Flowering Plants Pollen contains sperm Pollen contains sperm Produced by the stamen Produced by the stamen Ovary contains eggs Ovary contains eggs Found inside the flower Found inside the flower Pollen carries sperm to the eggs for fertilization Self-fertilization can occur in the same flower Cross-fertilization can occur between flowers

12. 12 Mendel’s Experimental Methods Mendel hand- pollinated flowers using a paintbrush Mendel hand- pollinated flowers using a paintbrush He could snip the stamens to prevent self-pollination He could snip the stamens to prevent self-pollination He traced traits through the several generations He traced traits through the several generations

13. 13 How Mendel Began Mendel produced pure strains by allowing the plants to self- pollinate for several generations

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16. 16 Mendels Crosses The 1 st cross produces all identical purple flowers. Mendel Crosses the offspring of the 1 st cross (F 1 ) and gets mostly purples and some white flowers in the F 2 generation.

17. 17 Mendel’s Experimental Results

18. 18 What Mendel Learns Traits are inherited as discrete units (explains why traits persist w/o being diluted or blended over generations. Traits are inherited as discrete units (explains why traits persist w/o being diluted or blended over generations.

19. 19 Mendels Laws Law of Segregation Law of Segregation Organisms inherit 2 copies of each gene, one from each parent. Organisms inherit 2 copies of each gene, one from each parent. Organisms donate only one copy of each gene in their gametes. Thus, the two copies of each gene segregate (separate) during gamete formation. Organisms donate only one copy of each gene in their gametes. Thus, the two copies of each gene segregate (separate) during gamete formation.

20. 20 Mendels Laws Law of Independent Assortment Law of Independent Assortment Allele pairs separate independently of eachother during gamete formation (meiosis). Allele pairs separate independently of eachother during gamete formation (meiosis). Traits appear to be inherited independently of one another. Traits appear to be inherited independently of one another.

21. 21 Law of Dominance In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. All the offspring will be heterozygous and express only the dominant trait. All the offspring will be heterozygous and express only the dominant trait. If R=round and r=wrinkled then RR x rr yields all Rr (round seeds) If R=round and r=wrinkled then RR x rr yields all Rr (round seeds)

22. 22 How Does It All Really Work?

23. 23 Genes A gene is a piece of DNA that directs a cell to make a certain protein. A gene is a piece of DNA that directs a cell to make a certain protein. Each gene has a locus, a specific position on a pair of homologous chromosomes. Each gene has a locus, a specific position on a pair of homologous chromosomes. Genes are expressed as traits Genes are expressed as traits or characteristics that may be passed on to offspring or Heredity.

24. 24 An allele is any alternative form of a gene occurring at a specific locus on a chromosome. An allele is any alternative form of a gene occurring at a specific locus on a chromosome. –Each parent donates one allele for every gene. –Homozygous describes two alleles that are the same at a specific locus (purebred). –Heterozygous describes two alleles that are different at a specific locus (hybrid).

25. 25 Genotype and Phenotype All of an organism’s genetic material is called the genome. All of an organism’s genetic material is called the genome. A genotype refers to the makeup of a specific set of genes. A genotype refers to the makeup of a specific set of genes. A phenotype is the physical expression of a trait. A phenotype is the physical expression of a trait. e.g. brown hair, blue eyes etc.

26. 26 Alleles can be represented using letters. A dominant allele is expressed as a phenotype when at least one allele is dominant. A dominant allele is expressed as a phenotype when at least one allele is dominant. A recessive allele is expressed as a phenotype only when two copies are present. A recessive allele is expressed as a phenotype only when two copies are present. Dominant alleles are represented by uppercase letters; recessive alleles by lowercase letters. Dominant alleles are represented by uppercase letters; recessive alleles by lowercase letters.

27. 27 Determining Genotypes Seed shape --- Round (R) or Wrinkled (r) Seed shape --- Round (R) or Wrinkled (r) Seed Color ---- Yellow (Y) or Green (y) Seed Color ---- Yellow (Y) or Green (y) Pod Shape --- Smooth (S) or wrinkled (s) Pod Shape --- Smooth (S) or wrinkled (s) Pod Color --- Green (G) or Yellow (g) Pod Color --- Green (G) or Yellow (g) Seed Coat Color ---Gray (G) or White (g) Seed Coat Color ---Gray (G) or White (g) Flower position---Axial (A) or Terminal (a) Flower position---Axial (A) or Terminal (a) Plant Height --- Tall (T) or Short (t) Plant Height --- Tall (T) or Short (t) Flower color --- Purple (P) or white (p) Flower color --- Purple (P) or white (p) 1. What is the genotype of a heterozygous round seed shape pea plant? 2. What is the genotype for a homozygous tall pea plant? 3. What is the genotype for a pea plant with a white flower?

28. 28 Seed shape --- Round (R) or Wrinkled (r) Seed shape --- Round (R) or Wrinkled (r) Seed Color ---- Yellow (Y) or Green (y) Seed Color ---- Yellow (Y) or Green (y) Pod Shape --- Smooth (S) or wrinkled (s) Pod Shape --- Smooth (S) or wrinkled (s) Pod Color --- Green (G) or Yellow (g) Pod Color --- Green (G) or Yellow (g) Seed Coat Color ---Gray (G) or White (g) Seed Coat Color ---Gray (G) or White (g) Flower position---Axial (A) or Terminal (a) Flower position---Axial (A) or Terminal (a) Plant Height --- Tall (T) or Short (t) Plant Height --- Tall (T) or Short (t) Flower color --- Purple (P) or white (p) Flower color --- Purple (P) or white (p) 1. What would be the genotype of a purebred pea plant with yellow seeds? 2. What would be the hybrid genotype for seed coat color? 3. What is the phenotype for a plant with a genotype of aa? 4. What is the phenotype for a plant with a genotype of Gg? 5. What is the phenotype for a plant with a genotype of YY?

29. 29 Punnett Squares A model for predicting all possible genotypes resulting from a genetic cross. A model for predicting all possible genotypes resulting from a genetic cross. They predict a likely outcome; they don’t “guarantee” a specific outcome. They predict a likely outcome; they don’t “guarantee” a specific outcome.

30. 30 Do a cross between a homozygous round seed plant a homozygous wrinkled seed plant. Round (R) Wrinkled (r) What genotypes and phenotypes would result?

31. 31 Do a cross between a heterozygous tall plant and heterozygous short plant (t). Tall (T) Short (t) What genotypes and phenotypes result?