What were the results of Mendel’s experiments, or crosses?

1. Section 1:Mendel’s Work • What were the results of Mendel’s experiments, or crosses? • What controls the inheritance of traits in organisms?

2. What is Genetics? • Genetics: the study of heredity • Heredity: the passing of physical characteristics from parents to offspring

3. The Father of Genetics • The field of Genetics was founded by Gregor Mendel, an Augustinian priest. • Between 1856 and 1863, Mendel cultivated and tested almost 30,000 pea plants. • The importance of Mendel's work was not discovered until almost 30 years after Mendel died.

4. Crossing Pea Plants • Gregor Mendel crossed pea plants that had different traits. The illustrations show how he did this.

5. Mendel’s Experiments • In all of Mendel’s crosses, only one form of the trait appeared in the F1 generation. However, in the F2 generation, the “lost” form of the trait always reappeared in about one fourth of the plants.

6. Dominant and Recessive Alleles • Mendel studied several traits in pea plants.

7. Dominant and Recessive Alleles • Today, scientists use the word “gene” to describe a piece of DNA that controls a trait.

8. Dominant and Recessive Alleles • The traits that Mendel studied in his pea plant experiments are controlled by different genes: • GENE • Seed Shape • Seed color • Seed coat color • Pod shape • Pod color • Flower position • Stem height

9. Dominant and Recessive Alleles • These genes usually have 2 or more alleles, or different forms of the gene: • GENE ALLELEALLELE • Seed Shape round wrinkled • Seed color yellow green • Seed coat color gray white • Pod shape smooth pinched • Pod color green yellow • Flower position side end • Stem height tall short

10. Dominant and Recessive Alleles • Some of these alleles are known as dominant. Others are known as recessive: • DOMINANTRECESSIVE • GENE ALLELEALLELE • Seed Shape roundwrinkled • Seed color yellow green • Seed coat color graywhite • Pod shape smoothpinched • Pod color greenyellow • Flower position sideend • Stem height tallshort

11. Dominant and Recessive Alleles • In a dominant allele, the trait always shows up as long as there is at least one dominant allele. Key T = tall t = short T T “pure tall” T t “hybrid tall”

12. Dominant and Recessive Alleles • In a recessive allele, the trait only shows up if both alleles are recessive. Key T = tall t = short t t “pure short”

13. Dominant and Recessive Alleles • Dominant alleles are always symbolized with capital letters. Recessive alleles are always symbolized with lower-case letters. Key for Height T = tall t = short Key for Seed Color Y = yellow seed color y = green seed color Key for Pod Color G = green pod color g = yellow pod color Key for Coat Color A = gray coat color a = white coat color

14. End of Section: Mendel’s Work

15. Section 2: Probability and Heredity • What is probability and how does it help explain the results of genetic crosses? • What is meant by genotype and phenotype? • What is codominance?

16. A Punnett Square • The diagrams show how to make a Punnett square. In this cross, both parents are heterozygous for the trait of seed shape. R represents the dominant round allele, and r represents the recessive wrinkled allele.

17. Probability and Genetics • In a genetic cross, the allele that each parent will pass on to its offspring is based on probability.

18. Phenotypes and Genotypes • An organism’s phenotype is its physical appearance, or visible traits. An organism’s genotype is its genetic makeup, or allele combinations.

19. Practicing Punnett Squares • T T x T T • t t x t t • T t x T t Key for Height T = tall t = short Key for Seed Color Y = yellow seed color y = green seed color Key for Pod Color G = green pod color g = yellow pod color

20. Practicing Punnett Squares • Y y x y y • Y Y x y y • g g x G g • G g x G g Key for Height T = tall t = short Key for Seed Color Y = yellow seed color y = green seed color Key for Pod Color G = green pod color g = yellow pod color

21. Homozygous vs. Heterozygous • Homozygous = 2 identical alleles • also called “pure” or “purebred” • Examples: T T t t Heterozygous = 2 different alleles also called “hybrid” Examples: T t

22. Codominance • In codominance, the alleles are neither dominant nor recessive. As a result, both phenotypes are expressed in the offspring.

23. Incomplete Dominance • In incomplete dominance, the contributions of both alleles are visible and do not overpower each other in the phenotype. As a result, both phenotypes look “mixed”.

24. Dihybrid Cross

25. Dihybrid Cross Key for Height T = tall t = short Key for Seed Color Y = yellow seed color y = green seed color Key for Pod Color G = green pod color g = yellow pod color

26. Dihybrid Cross

27. End of Section: Probability and Heredity

28. Section 3: The Cell and Inheritance • What role do chromosomes play in inheritance? • What events occur during meiosis? • What is the relationship between chromosomes and genes?

29. Meiosis • During meiosis, the chromosome pairs separate and are distributed to two different cells. The resulting sex cells have only half as many chromosomes as the other cells in the organism.

30. Punnett Square • A Punnett square is actually a way to show the events that occur at meiosis.

31. A Lineup of Genes • Chromosomes are made up of many genes joined together like beads on a string. The chromosomes in a pair may have different alleles for some genes and the same allele for others.

32. Human Chromosomes Humans have 23 pairs of chromosomes: 23 from their mother, and 23 from their father.

33. Human Chromosomes The first 22 pairs are organized and named according to their size: Chromosomes #1 are the largest, #2 are the second largest, etc.

34. Human Chromosomes The final pair of chromosomes (“X” and “Y”) are the sex chromosomes because they determine the gender of the person: XX = girl XY = boy

35. Sex Chromosomes The father is who determines the gender of the child since males need a “Y” chromosome, and only males have “Y” chromosomes. The mother can only give out an “X”, and both boys and girls have at least 1 “X” chromosome. Father Mother

36. End of Section: The Cell and Inheritance

37. Section 4: Genes, DNA, and Proteins • What forms the genetic code? • How does a cell produce proteins? • How can mutations affect an organism?

38. The DNA Code • Chromosomes are made of DNA. Each chromosome contains thousands of genes. The sequence of bases in a gene forms a code that tells the cell what protein to produce.

39. How Cells Make Proteins • During protein synthesis, the cell uses information from a gene on a chromosome to produce a specific protein.

40. Mutations • Mutations can cause a cell to produce an incorrect protein during protein synthesis. As a result, the organism’s trait, or phenotype, may be different from what it normally would have been.

41. Damages Made by Mutation • THEBIGBADCATATETHEBIGREDRAT

42. End of Section: Genes, DNA, and Proteins