1. TOPIC 22 - HEREDITY

2. Patterns of Inheritance Probability in Genetics

3. THINK – PAIR – SHARE

4. BenchmarkObjectives Students will understand the role of probability in genetics. Students will understand and be able to use the essential vocabulary of genetics. What are we learning today? SC.912.L.16.1 Use Mendel’s laws of segregation and independent assortment to analyze patterns of inheritance.

5. What is inheritance?  Inheritance is the passing on of characteristics from parents to offspring  In 1865, an Austrian monk named Gregor Mendel presented a paper on pea plant inheritance to the Natural History Society of Brünn.  The paper was virtually ignored for 30 years.  Years after Mendel’s death, his work was rediscovered. genetics, or the study of heredity  These patterns became the basis for a new branch of biology: genetics, or the study of heredity.

6. What is the essential question?  How are fractions, ratios and percentages related to the probability of inheritance?  Explain the difference between each pair: gene/allele, dominant/recessive, homozygous/heterozygous, genotype/phenotype.

8. How can we use probability to predict traits?  Probability is the likelihood that a particular event will occur.  Probabilities predict the average outcome of a large number of events.  Probability can be written as a percent, fraction, or a ratio.

9. Probabilities  The larger the number of outcomes, the closer the results will be to the predicted values.  This is why we repeat experiments many times

10. What essential vocabulary do I need to master?  Gene: Section of DNA that determines a trait.  Locus is the location of the gene on the chromosome  Alleles: are different forms of the same gene.  Each organism has two alleles for each trait  Homozygous: If the two alleles for a trait are the same (AA or aa)  Heterozygous: If the two alleles for a trait are different (Aa, hybrid)

11. What essential vocabulary do I need to master?  Dominant: Trait that is always observed in the offspring, even when a recessive allele is present.  Written as an uppercase letter.  Recessive: Trait only observed when two recessive alleles are present.  Written as a lowercase letter’

12. What essential vocabulary do I need to master?  Genotype - the gene combination, or genetic makeup, of an organism  Phenotype - the way an organism looks

13. What essential vocabulary do I need to master?  P or Parental generation: When doing genetic crosses, the name we call the original pair of organisms.  F 1 or First Filial generation: Offspring.  Mode of inheritance is Complete dominance

14. Mendel’s Principles  Principle of dominance: Some alleles are dominant and others are recessive.  Principle of segregation: When organisms produce gametes, the two alleles segregate from each other so that each gamete carries only a single copy of each “factor” (gene).  Principle of independent assortment: “Factors” for different traits can segregate independently during the formation of gametes.

15. Remember this was the reason for meiosis: to have only one of the homologous chromosomes (n=23) in the sperm or egg

16. Click above. I’m an animation for Sexual Variation

17. BenchmarkObjectives Students will use a Punnett square to predict the outcome of a monohybrid cross. Students will differentiate between simple dominant/recessive, incomplete dominance, and codominance. What are we learning today? SC.912.L.16.1 Use Mendel’s laws of segregation and independent assortment to analyze patterns of inheritance.

18. LET’S PRACTICE In roses, a gene that affects flower color has two alleles: red (R) and white (r). Two heterozygous plants are crossed. 1.What would be the genotype and phenotypes of the P and F 1 generations? 2.What is the probability that plants will be white? 3.Determine the ratio of red to white plants. ____

19. Answer to problem Two heterozygous plants –That means they have to have two alleles so both parents are Rr –Rr (mom) x Rr (dad) Because of the law of segregation the two alleles will segregate during meiosis I into different cells (sperm or egg can only get one allele from mom or one allele from dad, not both) –So mom can give a R and r »Place them on the Punnett square –Dad can also give R and r »Place them on the punnett square __R____r__ __R__RRRr __r__Rrrr The Squares in the Punnett square represent random fertilization between the eggs and sperm

20. LET’S PRACTICE A heterozygous German Shepherd with dark eyes (B) is bred with a homozygous German Shepherd with light eyes (b). What is the probability that they will have puppies with dark eyes? Explain your answer. ____

21. LET’S PRACTICE Black color in horses is dominant over chestnut color. If a homozygous black horse is mated to a chestnut horse, what percent of the offspring will be chestnut colored? Use a Punnett square to show how you arrived to your answer. ____

22. LET’S PRACTICE Cystic fibrosis is a recessive genetic disorder. Ron is homozygous dominant (FF) and Nancy is a carrier of cystic fibrosis. Use a Punnett square to predict the probability that one of their children will have cystic fibrosis? ____

23. LET’S PRACTICE In humans widow’s peak (W) is dominant over straight hairline (w). A heterozygous man for this trait marries a woman who is homozygous for hairline. What will be the genotype and phenotype of the first generation? ____

24. Day 2 Mode of Inheritance Incomplete Dominance Codominance

25. BenchmarkObjectives Students will describe how an X- or Y-linked gene affects the inheritance of traits. Students will describe multiple alleles patterns of inheritance What are we learning today? SC.912.L.16.1 Use Mendel’s laws of segregation and independent assortment to analyze patterns of inheritance.

26. What is incomplete dominance?  Crosses in which one allele is not completely dominant over another.  The heterozygous type is somewhere in between the two homozygous phenotype  An intermediate of the two (not red, not white, but pink). Heterozygous Homozygous Dominant Homozygous Recessive

27. How do we use superscripts in incomplete dominance patterns?  Superscripts are not exponents or additional alleles but labels to distinguish the two incomplete dominance alleles. Red flower C R Pink flower C R C W White flower C W

28. What is codominance?  Codominance inheritance: both alleles are expressed equally in the heterozygous type.(Both are equally dominant) Phenotype Red and white alleles are both expressed. NO MIXING

29. Incomplete dominance (A) or Codominance (B) 1)The phenotype of the heterozygote is intermediate from the parent’s phenotype. 2)Two checkered (black and white) chicken are crossed. They produce offspring with three phenotypes: black, white, and checkered. 3)Two gray rabbits are crossed. They produce offspring with three phenotypes: black, white, and gray. 4)A red-flowered plant is crossed with a white-flowered plant. All of the offspring are pink. 5)A cross between a purebred animal with red hairs and a purebred animal with white hairs produces and animal that has both red hairs and white hairs.

30. LET’S PRACTICE In snapdragons, a gene that affects flower color has two alleles: red and white. In heterozygous individuals, the phenotype is pink. Show a cross between two pink snapdragons and give the expected genotype and phenotype. What is their mode of inheritance? ____

31. LET’S PRACTICE In shorthorn cattle, coat color may be red, white, or roan. In roan cattle, their coats are a mixture of red and white hairs, although the animals appear a light rust color from a distance. Show a cross between two roan cattle and give the expected genotype and phenotype. What is their mode of inheritance? ____

32. Patterns of Inheritance Sex-linked Inheritance Multiple Alleles Inheritance

33. Think – Pair - Share 1.What is shown in the image below? 2.What is their importance in heredity? 3.What are the parts of one of these chromosomes? 4.Can you see the individual genes on the chromosomes?

34. What is a karyotype?  A karyotype shows the complete diploid set of chromosomes grouped together in pairs, arranged in order of decreasing size.  Two chromosomes are known as the sex chromosomes because they determine an individual’s sex.  Females have two copies of the X chromosomes. (44 + XX= 46)  Males have one X chromosome and one Y chromosome. (44 + XY=46)  The other 22 pairs are called autosomes.

35. What is sex-linked inheritance?  Traits controlled by genes located on sex chromosome are called sex-linked traits  Genes are on the X but not on the Y  Y chromosome is much smaller and missing genes that are on the X  Males are affected more often because they only get one allele instead of two. If the one allele is bad they get the sex-linked trait.  Females are less likely to get sex-linked traits because they get two alleles and the probability that both are bad alleles is less.

36. What is sex-linked inheritance? Color Blindness Alleles Normal (C)→ X C Affected (c) → X c Color Blindness Genotype/Phenotypes by Sex X C X C X C X c X c X c Normal Female Normal Female (carrier) Color Blind Female X C YX c Y Normal male Color Blind Male  The alleles for sex-linked traits are written as superscripts of the X and Y chromosomes.  Color Blindness is a sex-linked trait Why doesn’t the Y get a superscript? Question: Mom is normal (homozygous dominant) and dad has color blindness, what will be the genotype and phenotype of the offspring?

37. What is sex-linked inheritance? Hemophilia Alleles Normal (H)→ X H Affected (h) → X h Hemophilia Genotype/Phenotypes X H X H X H X h X h X h X H YX h Y Hemophilia is a sex-linked trait that does not allow a person’s blood to clot properly causing prolong bleeding that can become life threatening Question: If your father is normal and your mom is a carrier, what will be the genotype and phenotype of their offspring? What is the probability of having a daughter with the trait? The probability that a son will have it? The percentage of carriers?

38. GUIDED PRACTICE The colorblindness gene (X b ) is recessive to the gene for normal sight (X B ). Construct a Punnett square to show a cross between a father with normal vision and a mother who is colorblind. 1.What percent of the children have normal vision? 2.What percent of the daughters are carriers? 3.What is the probability of having a sick son? 4.What is the probability of having a healthy daughter? ____

39. LET’S PRACTICE Hemophilia is a recessive sex-linked trait (X h ) caused by a defective gene. The blood of individuals with this condition does not clot properly. Without injections of synthetic clotting factors, hemophiliacs are at risk of dying due to excessive bleeding. Make a Punnett square to show a cross between an affected male and a female who is heterozygous. 1.Give the expected genotype and phenotype. 2.How likely are they to have a sick child? ____

40. What is multiple allele inheritance?  In multiple allele inheritance there is more than two possible alleles in a population.  This does not mean that an individual can have more than two alleles.  The alleles for multiple alleles traits are written as superscripts of the letter used.

41. How do multiple alleles and codominance determine blood type?  There are three alleles for the ABO gene: I A, I B, and i.  Alleles I A and I B are codominant.  Produce molecules on the surface of RBC.  The i allele is recessive.  Produce no molecule on RBC.  Fur color in animals isanother example of multiple alleles

42. Four alleles exist for the C (fur color) gene. –The wild-type version, C + C +, is expressed as brown fur –The chinchilla phenotype, c ch c ch, is expressed as black- tipped white fur –The Himalayan phenotype, c h c h, has black fur on the extremities and white fur elsewhere –The albino, or “colorless” phenotype, cc, is expressed as white fur. In cases of multiple alleles, dominance hierarchies can exist. In this case, the wild-type (Brown) allele is dominant over all the others, chinchilla is dominant over Himalayan and albino, and Himalayan is dominant over albino.

43. GUIDED PRACTICE Is it possible for a woman with type AB blood and a man with type B blood to have a child with type O blood? What possible blood types can their children have? Use a Punnett square to support your answer.

44. Polygenic Inheritance One trait is controlled by many genes In humans –Skin Color –Height –Weight –Hair color It gives a bell curve –Most people are in the middle while a few are at the extremes

46. What is the essential question? Colorblindness is a recessive, sex-linked trait. A woman and a man, both with normal vision, have three daughters with normal vision. One of the daughters marries a man with normal vision, and they have a son who is colorblind. Part A – Which parent of the son is the carrier of the trait? Explain your answer. Part B – What is the likelihood that the children of a woman heterozygous for colorblindness and a colorblind man will express the trait? Explain your answer.

47. Patterns of Inheritance Dihybrid Crosses

48. BenchmarkObjectives Students will use a Punnett square to predict the outcome of a dihybrid cross What are we learning today? SC.912.L.16.1 Use Mendel’s laws of segregation and independent assortment to analyze patterns of inheritance.

49. What is the essential question? 1.On the average, each human has about six recessive alleles that would be lethal if expressed. Why do you think that human cultures across the world have laws against marriage between close relative? 2.Why is it possible to have a family of six girls and no boys, but extremely unlikely that there will be a public school with 500 girls and no boys?

50. What is a dihybrid cross?  A dihybrid cross involves a study of inheritance patterns for organisms differing in two traits.  Mendel invented the dihybrid cross to determine if different traits of pea plants were inherited independently. He didn’t know about chromosomes

51. Let's do it –Cross a pea plant RrYy x RrYy When crossing two traits you must use both laws –Law of independent assortment –Law of segregation ____ RrYy x RrYy RY Ry rY ry Order is important do orange lines first, than blue, than green and finally red. R = Round. r= wrinkly Y = Yellow. y= Green

52. LET’S PRACTICE RYRyrYry RY RRYYRRYyRrYYRrYy Ry RRYyRRyyRrYyRryy rY RrYYRrYyrrYYrrYy ry RrYyRryyrrYyrryy Given the following information: Predict the genotype and/or phenotype of the following. 3? 1? 2? 4? Shape RSmooth rWrinkled Color YYellow yGreen

53. CHECK YOUR UNDERSTANDING 1.List all the possible genotypes of a pea plant with round/smooth (R) and yellow (Y) seeds. What is their percent or fraction? 2.List all the possible genotypes of pea plant with smooth (R) and green (y) seeds. What is their percent or fraction? 3.List all the possible genotypes of pea plant with wrinkled (r) and yellow (Y) seeds. What is their percent or fraction? 4.List all the possible genotypes of a pea plant with wrinkled (r) and green (y) seeds. What is their percent?

54. LET’S PRACTICE AaBb x AABb ____

55. LET’S PRACTICE In rabbits, the coat color black dominant (B) over brown (b). Short hair is dominant (S) over long (s). In a cross between a homozygous black short-haired male and a brown long-haired female, what would be the ratios for genotype and phenotype of the F 1 generation? ____ ___ ____

56. Pedigree Squares are Males Circles are Females Shaded Widows peak vs. Unshaded no widows peak

60. IN REVIEW –Complete dominance (Mendel's genetics) Genotype ratio (starting with true breeders) –F 1 : 1 or 100% heterozygotes –F 2 : 1:2:1 (dominant to recessive) Phenotype ratio (starting with true breeders) –F 1 : 1 or 100% Dominant trait –F 2 : 3:1 (dominant to recessive) –Incomplete dominance Genotype ratio (starting with true breeders) –F 1 : 1 or 100% heterozygotes –F 2 : 1:2:1 Phenotype ratio (starting with true breeders) –F 1 : 1 or 100% Intermediate (heterozygotes) –F 2 : 1:2:1 –Codominance Genotype ratio (starting with true breeders) –F 1 : 1 or 100% heterozygotes –F 2 : 1:2:1 Phenotype ratio (starting with true breeders) –F 1 : 1 or 100% checkered (heterozygotes) –F 2 : 1:2:1

61. Review: MODES OF INHERITANCE Complete Dominance Incomplete Dominance Codominance Sex Linked –X-linked