The Work of Gregor Mendel:

1. The Work of Gregor Mendel: Monohybrid, Dihybrid, Incomplete, Codominance, Multiple Alleles, Polygenic Traits

2. Genetics: study of hereditary • Every living being- plant, animal, microbe or human being, has a set of characteristics inherited from its parent or parents. • Genetics: study of hereditary

3. Gregor Mendel’s Peas: • Austrian Monk in charge of the garden, Studied peas

4. What he knew: • fertilization- during sexual reproduction a male sperm (pollen) and female egg (ova) joined which produced a new cell, which began to develop into a tiny embryo encased within a seed. • When Mendel took control of the garden, he had a garden full of self-breeding garden peas which were true-breeding

5. True-breeding- • pure genes, if allowed to self pollinate, these plants would produce identical copies of themselves.

6. What he had to work with • One stock of seeds: produced Tall plants, • One stock of seeds: produced Short Plants, • One line produced: green Seeds, • Another line produced: yellowSeeds

7. cross pollination • Basis of Mendel’s Experiments: Tall, Short, green Seeds, yellow seeds • He wanted to cross breed these plants called cross pollination

8. Genes and Dominance: • Mendel studied 7 different pea plant traits • Trait: a specific characteristic, such as seed color or height

9. Mendel crossed these plants and studied their offspring • He called each of the original plants the P (Parental) generation

10. F1 generation • He called the offspring, F1 or “first filial” generation • Filius and filia are the Latin words for “son” and “daughter” • Therefore the child in the picture below is the F1 generation of those parents

11. Hybrids • The offspring of crosses between parents with different traits are called hybrids • Ex: toyota prius

12. Hybrids in other areas • Mythology: Centaurs • Biology: Zeedonk, Liger

13. So, what were the results? Did they have a mixture of all the traits? • NO, all the hybrids had the characteristics of only ONE of the parents. • In each cross, the character of the other parent seemed to disappear!

14. First Conclusion: • biological inheritance is determined by factors that are passed from one generation to the next • Today, we called these GENES • Different forms of a gene are called Allele

16. Second conclusion: Principle of Dominance • P of D: states that some alleles are dominant and others are recessive • An organism with a dominant form will ALWAYS show the trait

17. Mendel’s Findings • Tall plant was Dominant and Short plant was recessive/ • Yellow seeds Dominant and green seeds are recessive

19. Some common human dominant traits

20. Segregation: • Mendel wanted to know what happened to the recessive traits. Did they disappear? • He took the F1 generation and crossed them with one another and made the F2 generation

22. F2 generation: • the recessive traits reappeared • ¼ or 25% of all the plants had the recessive traits

24. He concluded the • F1 plants produced gametes (sex cells), the 2 alleles segregated from one another so that each gamete carried a single copy of the gene • In the F1 generation, each gamete had 1 copy of the Tall gene and one copy of the short gene.

27. Genetics and Probability: • Probability: the likelihood that an event will occur • Coin toss: 2 possibilities: head or tails • The probability or chances are equal, 1 in 2 chance • That is ½ or 50% chance • If you flip a coin 3 times in a row what are the chances that you will get heads every time: ½ x ½ x ½ = 1/8 1 in 8 chance of flipping heads 3 times in a row!

28. So what? • The principles of probability are used to predict the outcomes of genetic crosses

29. Punnett Squares • the gene combinations that might result from a genetic cross can be determined by drawing a diagram known as a Punnett Square

30. Very important terms to know! • Homozygous: 2 identical alleles (TT or tt) considered true-breeding • Heterozygous: 2 different alleles (Tt) considered Hybrids • Phenotypes: physical characteristics, like tall or short • Genotypes: genetic characteristics like TT, Tt, or tt

32. Tutorial • The figure represents a monohybrid cross of F1-hybrid plants. • Both parent plants are heterozygous (Ss) for an allele that determines seed shape. • Presence of the dominant allele (S) in homozygous (SS) or heterozygous (Ss) plants results in spherical seeds. • Homozygous recessive (ss) plants have dented seeds.

33. Setting up a Punnett square • 1.Set up a 2 by 2 Punnett square.

34. 2. Write the alleles for parent 1 on the left side of the Punnett square. • Each gamete will have one of the two alleles of the parent. • In this particular cross, half of the gametes will have the dominant (S) allele, and half will have the recessive (s) allele.

35. 3. Write the alleles from parent 2 above the Punnett square. • For this heterozygous parent (Ss), half of the gametes will have the dominant (S) allele, and half will have the recessive (s) allele.

36. 4. Fill the squares for parent 1. • Fill each square with the allele from Parent 1 that lines up with the row.

37. 5. Fill the squares for parent 2. • Fill each square with the allele from Parent 2 that lines up with the column.

38. Interpreting the results of a Punnett square • We now have the information for predicting the outcome of the cross. • The genotypes in the four boxes of the Punnett square are each equally likely to occur among the offspring of this cross. • We may now tabulate the results.

39. Genotypes that resulted from this monohybrid cross (Ss x Ss) • 25% 50% 25% • homozygousheterozygoushomozygous dominant dominant recessive

40. Phenotypes that resulted from this monohybrid cross (Ss x Ss)

41. Independent Assortment: Dihybrid Crosses • 2 factor Cross • Mendel crossed true breeding plants that produced only round yellow peas (RRYY) with plants that produced wrinkled green peas (rryy) • All the F1: round yellow peas

42. Showed that the allele for yellow and round peas are dominant • Provided the hybrid plants for the F1 cross to produce the F2 generation • F2: RrYy • Found a grand mix of traits proving that the genes practiced independent assortment meaning that the seed shape and color are independent of one another

43. F2 results// • 9:3:3:1 • 9 yellow and round, 3 green and round, 3 yellow and wrinkled, 1 green and wrinkled

45. Tutorial: Dihybrid Crosses • Determine all possible combinations of alleles in the gametes for each parent. • Half of the gametes get a dominant S and a dominant Y allele; the other half of the gametes get a recessive s and a recessive y allele. • Both parents produce 25% each of SY, Sy, sY, and sy.

46. 1. Punnett square. • Since each Parent produces 4 different combinations of alleles in the gametes, draw a 4 square by 4 square punnett square.

47. 2. Place in Gametes from Parent 1 • List the gametes for Parent 1 along one edge of the punnett square.

48. 3. Place Gametes from Parent 2 • List the gametes for Parent 2 along one edge of the punnett square.

49. 4. Fill in Alleles from Parent 1 • Fill out the squares with the alleles of Parent 1.

50. 5. Fill in Alleles from Parent 2 • Fill out the squares with the alleles from Parent 2. • The result is the prediction of all possible combinations of genotypes for the offspring of the dihybrid cross, SsYy x SsYy.