Heredity (Inheritance) and Genetics

1. Heredity (Inheritance) and Genetics

2. Heredity • Is it possible for two parents with blue eyes to have a brown eyed child?

3. Heredity 2. Is it possible for two parents with brown eyes to have a blue-eyed child?

4. Heredity • Rebecca and Leah look so much alike that everyone says they must be sisters. What kind of test should we do to determine if they are sisters?

5. Review What do you know about each of the following: • DNA • Genes • Chromosomes

6. Chromosomes have genetic information and are passed to offspring Dividing onion cells chromosomes chromosomes cell wall nucelus

7. Chromosomes have genetic information and are passed to offspring Human chromosomes stained with a special chemical and viewed under a high-powered microscope

8. What exactly are chromosomes? How do chromosomes contain genetic information?

9. Chromosome structure- DNA • Chromosomes = long pieces of DNA

10. Chromosome structure- genes • Parts of chromosomes are called genes • Genes help determine your characteristics • what are some example characteristics? Human chromosome # 7 • Contains about 1,800 genes • Contains over 150 million nucleotides Link to view genes and DNA sequence

11. Trait – a characteristic of an organism • Example: “flower color” Gene – part of a chromosome that helps determine a specific trait • Example: “flower color gene” Allele – a form of a gene • Example: • One allele is the “blue” form of the gene • One allele is the “red” form of the gene

12. Review How do the terms trait, chromosome, gene, and allele relate to each other?

13. Chromosomes come in pairs Cut out from picture and match each in pairs. This is called a KARYOTYPE

14. Homologous chromosomes? • Humans = 23 chromosome pairs, or 46 total. We think we have about 20,000 genes. • Pea flower = 7 chromosome pairs (14 total) • Fruit fly = 4 chromosome pairs (8 total) 13,601 genes identified so far! • What part of a chromosome do you think is homologous or identical? • What effect do these differences have on characteristics?

15. Chromosomes come in pairs • You get one copy of a chromosome from one parent and one copy of a chromosome from the other parent. • This pair of chromosomes is called a “homologous pair” because they have the same genes on them - flower color gene Flower chromosome 3 From Dad From Mom

16. Chromosomes come in pairs IMPORTANT: homologous pairs have the same genes, but they are NOT IDENTICAL • Alleles can be different flower color gene “Blue” allele of flower color gene “Red” allele of flower color gene From Dad From Mom

17. Chromosomes are shuffled When homologous chromosomes are reunited following meiosis and sex, the combination of Alleles can be different flower color gene “Blue” allele of flower color gene “Red” allele of flower color gene From Dad From Mom

18. The combination of alleles determines the observed characteristics RED allele BLUE allele RED allele BLUE allele BLUE allele RED allele Chromosome combination Allele combination red, red red, blue (or blue, red) blue, blue Observed characteristic RED ? BLUE

19. Dominant and recessive alleles Only one red allele is needed for the flower to look red. • Scientists call this a DOMINANT allele Two blue alleles are needed for the flower to look blue. • Scientists call this a RECESSIVE allele

20. Symbols used for alleles • The traditional symbols used for alleles are big and small letters • The letter chosen usually refers to the dominant allele Example: R = Red allele r = Blue allele

21. The combination of alleles determines the observed characteristics RED allele BLUE allele RED allele BLUE allele BLUE allele RED allele Chromosome combination Allele combination red, red red, blue (or blue, red) blue, blue Observed characteristic RED RED BLUE

22. The combination of alleles determines the observed characteristics R R R r r r Chromosome combination Allele combination RR Rr rr Observed characteristic RED RED BLUE

23. Phenotype – the observed (or measurable) trait of an organism that relates to one gene Genotype – the two alleles that an organism has for a trait Example: Trait = “flower color” Phenotype = “RED” or “BLUE” Genotype = “RR” or “Rr” or “rr”

24. The combination of alleles determines the observed characteristics R R R r r r Chromosome combination Allele combination RR Rr rr Observed characteristic RED RED BLUE

25. The combination of alleles determines the observed characteristics R R R r r r Chromosome combination GENOTYPE RR Rr rr PHENOTYPE RED RED BLUE

26. Homozygous – the two alleles are the same • RR and rr are homozygous genotypes Heterozygous – the two alleles are different • Rr is a heterozygous genotype

27. Review • What are homologous chromosomes? • What part of a chromosome do you think is homologous or identical. • What is a dominant allele? • What is a recessive allele? • What is homozygous? • What is heterozygous? • What is phenotype? • What is genotype?

28. Modeling Genetic crosses • Documents and Models how genetic information is passed along. • Accounts for patterns seen in a pedigree • Makes predictions about the phenotypes and genotypes seen in the next generation

29. Possible combinations of inherited chromosomes/genes Dad Mom Parents R r R r X R R Possible Offspring Order doesn’t matter, these two are the same (Rr) R r r R r r What are all possible genotypes produced from the parents? RR, Rr, rr

30. Punnett squares organize all possible offspring combinations Dad Mom R r R r X Your turn: What are all possible genotypes produced by crossing Rr with rr? R r R RR Rr r Rr rr

31. Punnett squares predict ratios of all genotypes and phenotypes produced Genotypic ratio = Phenotypic ratio = 1RR: 2Rr:1rr or 25%RR:50%Rr:25%rr 3 Red:1 blue or 75% Red:25% Blue

32. Predicted ratios determine the probability of each genotype/phenotype 1 out of 4 possibilities is rr = 25% chance of rr • What is probability of Rr? • How many out of 4 are red? • What is the probability of red? • What is the probability of blue? Genotypic ratio = 1RR: 2Rr:1rr Phenotypic ratio = 3 Red:1 blue

33. Punnett square practice Calculate the predicted genotypic and phenotypic ratios Calculate the probability of each genotype and phenotype • Hh X HH – H(hairy) is dominant over h(not hairy) • Gg X gg – G(green sepals) is dominant over g(yellow sepals)

34. Review • What is the relationship between genotype and phenotype? • What is the relationship between Homozygous and Heterozygous • Give an example of a heterozygous genotype for height (T = tall; t = short): • Give an example of a homozygous genotype for height (T = tall; t = short): • What is the phenotype of a plant heterozygous for the height gene?

35. Dihybrid cross • Used to predict the combinations of 2 traits contained on two separate chromosomes. • For example for the traits of stripes and tails on a cat: • Two double-heterozygous striped, with tail cats are crossed. • How many offspring will be striped and have a tail, how many will be striped with no tail, how many will be plain with a tail…

36. Practice • Construct a Punnett Square for each of the following crosses. • Remember: the two traits are on two different chromosomes. • Write the Genotypic and Phenotypic Ratio below the Punnett Squares. • SsTt X SsTt • SSTt X SsTt • SSTT X SsTt S = striped s = plain T = tail t = no tail

37. SsTt X SsTt S = striped s = plain T = tail t = no tail

38. SsTt X SsTt S = striped s = plain T = tail t = no tail

39. SsTt X SsTt S = striped s = plain T = tail t = no tail

40. SsTt X SsTt S = striped s = plain T = tail t = no tail

41. SsTt X SsTt S = striped s = plain T = tail t = no tail

42. SsTt X SsTt S = striped s = plain T = tail t = no tail Genotypes: 1 SSTT: 2 SSTt: 1 SStt: 2 SsTT: 4 SsTt: 2 Sstt: 1 ssTT: 2 ssTt: 1 sstt Phenotypes: 9 striped, tail : 3 striped, no tail : 3 plain, tail : 1 plain, no tail

43. SSTt X SsTt S = striped s = plain T = tail t = no tail If they are the same as above you do NOT have to rewrite the genotype Genotypes: 1 SSTT: 1SSTt: 1SsTT: 1SsTt: 1SSTt: 1SStt: 1SsTt: 1Sstt Phenotypes: 6 Striped with Tail: 2 Striped with no tail (3:1 reduced)

44. SSTT X SsTt S = striped s = plain T = tail t = no tail Same Genotypes: 1 SSTT: 1 SSTt: 1 SsTT: 1 SsTt Phenotypes: 4 Striped Tail (100%)

45. Inheritance quiz

46. #1 #2 #3 #1 #2 #3 • What is the trait for the flowers? __________________ • What is the trait for the animals? __________________ • What is the recessive allele for the flower trait? _______ • What is the dominant allele for the animal trait? _______ • Which flower is heterozygous? ___________ • Which animal is homozygous dominant? __________ • What is the genotype of flower #1? ________________ • What is the genotype of animal #2? ________________ • What is the phenotype of flower #2? ________________ • What is the phenotype of animal #3? ________________ Width/thickness/petals Type of Hair f (or narrow) H (or straight) #1 #2 Ff HH Wide Straight Hair

47. Punnett Square F f Genotypic ratio: Phenotypic ratio: 1 Ff : 1 ff (2 Ff : 2 ff is OK) f f Ff ff 1 fat : 1 skinny (2 fat : 2 skinny is OK) Ff ff

48. Review In flowers, red color (R) is dominant to blue color (r). • What possible genotypes produce a blue flower? What possible genotypes produce a red flower? • Explain how you could determine the actual genotype of a red flower by performing a genetic cross many times and looking at the offspring phenotypes.

49. Review • How many sets of your 23 chromosomes do you have (1, 2, 3, or 4?) • How many of each type of chromosome is inherited from your mom? • How many of each type of chromosome is inherited from your dad?

50. Original cell Sperm or egg cells If parents have two copies of each chromosome, how do they pass on only one to their offspring? • MEIOSIS is the process of cell division that decreases the number of chromosomes to make sperm or egg cells