Genetics

1. Genetics Reference: Biology Textbook, Chapter 11: Introduction to Genetics

2. Gregor Mendel • In 1865, GregorMendel published studies of inheritance in pea plants. • During sexual reproduction, male and female gametes (reproductive cells; n) join to form a zygote(2n) in the process known as fertilization.

3. Heredity is… • Controlled by “factors.” (known as genes on chromosomes) • Passed from generation to generation. • Predicted Outcomes through Probabilityusing Punnett Squares.

4. 1902 – Chromosome Theory of Heredity • Genes (Mendels “factors”) are located on chromosomes. • The different forms (variations) of a gene are called Alleles. • This is the basis for the modern science of Genetics.

5. Genetic Principles • Dominant and Recessive • Dominant = seen when present on the chromosome • Recessive = only seen when dominant allele is not present on the chromosome • Law of Segregation and Independent Assortment • Randomness • Placement of chromosomes within the process of meiosis • Genotype and Phenotype • Genotype – using letters to represent the trait’s alleles • Ex: Flower Color - FF, Ff, ff • Phenotype – using descriptive words (adjectives) to describe the trait’s alleles. • Ex: Flower Color – Purple or white • Homozygous and Heterozygous • Homozygous = same allele variations (TT, tt) • Heterozygous = difference allele variations (Tt)

6. Genes VS Alleles

7. Genes VS Alleles

8. R.C. Punnett • In 1905, R.C. Punnett introduced the Punnett square. • Punnett squares can be used to predict and compare the genetic variations that will result from a cross (pg. 268).

9. Using Punnett Squares Yellow pea seed (Y) is DOMINANT to green (y). Genotype: YY xyy Phenotype: Yellow x green

10. Using Punnett Squares Yellow pea seed (Y) is DOMINANT to green (y). Genotype: YY xyy Phenotype: Yellow x green

11. Using Punnett Squares Yellow pea seed (Y) is DOMINANT to green (y). Genotype: YY xyy Phenotype: Yellow x green

12. Using Punnett Squares Yellow pea seed (Y) is DOMINANT to green (y). Genotype: YY xyy Phenotype: Yellow x green

13. Using Punnett Squares Yellow pea seed (Y) is DOMINANT to green (y). Genotype: YY xyy Phenotype: Yellow x green

14. Using Punnett Squares Yellow pea seed (Y) is DOMINANT to green (y). Genotype: YY xyy Phenotype: Yellow x green

15. Using Punnett Squares Yellow pea seed (Y) is DOMINANT to green (y). Genotype: YY xyy Phenotype: Yellow x green

16. Using Punnett Squares Yellow pea seed (Y) is DOMINANT to green (y). Genotype: YY xyy Phenotype: Yellow x green

17. Using Punnett Squares Yellow pea seed (Y) is DOMINANT to green (y). Genotype: YY xyy Phenotype: Yellow x green

18. Using Punnett Squares Yellow pea seed (Y) is DOMINANT to green (y). Genotype: YY xyy Phenotype: Yellow x green All (100%) offspring in F1 Generation are Yellow hybrids.

19. Monohybrid Cross Yy x Yy Yellow x Yellow

20. Monohybrid Cross Genotype: Yy x Yy Phenotype: Yellow x Yellow

21. Monohybrid Cross Genotype: Yy x Yy Phenotype: Yellow x Yellow

22. Monohybrid Cross Genotype: Yy x Yy Phenotype: Yellow x Yellow

23. Monohybrid Cross Genotype: Yy x Yy Phenotype: Yellow x Yellow

24. Monohybrid Cross Genotype: Yy x Yy Phenotype: Yellow x Yellow

25. Monohybrid Cross Genotype: Yy x Yy Phenotype: Yellow x Yellow

26. Monohybrid Cross Genotype: Yy x Yy Phenotype: Yellow x Yellow

27. Monohybrid Cross Genotype: Yy x Yy Phenotype: Yellow x Yellow

28. Monohybrid Cross Genotype: Yy x Yy Phenotype: Yellow x Yellow

29. Monohybrid Cross Genotype: Yy x Yy Phenotype: Yellow x Yellow Phenotypic Ratio: 75% (3/4) offspring are Yellow; Ratio is 3:4 (Yellow : total) 25% (1/4) offspring are green; Ratio is 1:4 (green : total) Genotype Ratio: 25% (1/4) offspring are YY, Ratio is 1:4 (homozygous dominant : total) 50% (2/4) offspring are Yy, Ratio is 1:2 (heterozygous : total) 25% (1/4) offspring are yy, Ratio is 1:4 (homozygous recessive : total)

30. Dihybrid Cross • Round pea seed (R) is dominant to wrinkled pea seed (r). • FOIL: YyRrYR, Yr, yR, yr • (These are the possible genotypic combinations)

31. Dihybrid Cross Round pea seed (R) is dominant to wrinkled pea seed (r).

32. Dihybrid Cross Round pea seed (R) is dominant to wrinkled pea seed (r).

33. What is the probability that the plant will produce: Yellow, Round Peas: Yellow, Wrinkled Peas: Green, Round Peas: Green, Wrinkled Peas:

34. What is the probability that the plant will produce: Yellow, Round Peas: 9/16 Yellow, Wrinkled Peas: 3/16 Green, Round Peas: 3/16 Green, Wrinkled Peas: 1/16

35. To find the probability that two different events will happen at the same time, multiply the probabilities of each event happening separately.

36. To find the probability that two different events will happen at the same time, multiply the probabilities of each event happening separately. Probability of offspring having YELLOW pea seeds: ¾ Probability of offspring having ROUND pea seeds: ¾ Probability of offspring having BOTH YELLOW AND ROUND PEAS: ¾ X ¾ = 9/16

37. Trihybrid Cross • Tall Stem (T) is dominant to short stem (t). • The probability of producing tall stems in a monohybrid cross is: • What is the probability that the offspring in a trihybrid cross will be Yellow, Round, and Tall?

38. Trihybrid Cross • Tall Stem (T) is dominant to short stem (t). • The probability of producing tall stems in a monohybrid cross is: ¾ • What is the probability that the offspring in a trihybrid cross will be Yellow, Round, and Tall? ¾ X ¾ X ¾ = 27/64