1. Genetics The scientific study of inheritance Heredity – the transmission of traits from one generation to the next.

2. Early theory of inheritance the “Blending Theory” Offspring were a blending of both parents Helped to explain the similarities between parents and offspring.

3. Gregor Mendel – Austrian Monk 1822-1884 Mendel discovered the basic principles of heredity using pea plants Came up with the “particulate” hypothesis – individuals inherit units or particles (genes) from their parents.

4. What makes a good experimental organism for genetic study? –Many traits –Reproduce Sexually –Crosses can be controlled –Have short life cycles/short gestation –Produce large number of offspring –Easy to handle in a laboratory Why Peas?

5. Which organisms would be useful? Why or Why Not? Humans Fruit flies Bacteria Oak trees Dogs Mice

6. Mendel studied 7 different pea plant characteristics (or characters). Character – is a heritable feature, such as flower color that varies among individuals Trait – Different varieties of a character sometimes they are used synonymously – as may occur within this chapter.

7. Pea plant Characteristics –Seed shape –Seed color –Seed coat color –Pod shape –Pod color –Flower position –Plant height Each character had 2 contrasting traits. For example, seed color is either yellow or green, plant height is tall or short.

8. Mendel’s Experiment http://safeshare.tv/v/MWkFxWXHT nwhttp://safeshare.tv/v/MWkFxWXHT nw Pea flowers have both male and female parts Reproduce by self-pollination –Pollen from the male part of the flower fertilizes the female egg cells of the same flower. The seeds produced inherit all their characteristics from one parent.

9. Mendel began his experiments with true- breeding (a.k.a pure breed) pea plants. –True-breeding plants, when self pollinated produce offspring identical to the parent. He produced seeds by joining male and female reproductive cells from two different plants. This resulted in a hybrid plant –The offspring of a cross between parents with different traits.

10. Here’s what Mendel did: Cross-Pollination P generation The offspring of the P generation are called the F1 generation

11. What were the F 1 hybrids like? Did the characters blend? –No, the offspring all had the character of only one parent. –Did the other character disappear?

12. What happened to the white trait? Was it lost? Mendel allowed the F1 generation to self-pollinate and produce a F2 generation. The white character came back. These purple plants self- pollinate and produce offspring.

13. Mendel’s conclusions One… Inheritance is determined by factors that are passed on from one generation to the next These factors are now called genes Genes exists in contrasting forms The alternative form of a gene are called alleles

14. Alleles alternate versions of a gene In this example, Flower color is the trait, the Alternate versions of flower color are Purple and White Figure 14.4 Allele for purple flowers Location for flower-color gene Homologous pair of chromosomes Allele for white flowers Chromosome from Dad Chromosome from Mom

15. Mendel’s conclusions Two…. The principle of dominance some alleles are dominant and others are recessive Dominant – the trait that is always expressed Recessive – will only be expressed when both the alleles are recessive

16. How did Mendel explain this? The Law of Segregation –An organism will inherit 2 alleles for a particular trait –The two alleles for a character separate (segregate) during gamete formation and end up in different gametes.

17. If an organism receives… Two dominant alleles = homozygous dominant Two recessive alleles = homozygous recessive One dominant allele and one recessive allele = heterozygous –The individual will express the dominant trait.

18. Expected and Observed Results Knowing the genes of living things helps to predict what traits their offspring could have.

19. Punnett Square: Used to Predict and compare the genetic variations that will result from a cross Also shows how alleles segregate

20. The Punnett Square Shows how genes can combine when egg and sperm join. Letters are used to represent the alleles for a gene (a specific trait) P p p

21. Punnett Square A Capital letter is used to represent a dominant allele, such as P (purple) A lower case letter is used to represent a recessive allele, such as p (white) –It helps if the letters look different in the capital and lower case form. (Ss – not good)

22. Terms to Know Genotype – what’s written in the genes (PP) Phenotype – the physical appearance (purple) Homozygous – having 2 identical alleles (PP or pp) –Homozygous dominant and recessive Heterozygous – having 2 different alleles (Pp)

23. Terms to Know (continued) Dominant – form of a gene that is expressed (ex. RR or Rr) –Homozygous dominant or heterozygous Recessive – gene that is masked – is only expressed as homozygous recessive (ex. rr)

24. Drawing the Punnett Square Example: Purple and White flowers One set of alleles goes across the top PP The other set goes down the side p p

25. Drawing the Punnett Square True breeding Purple (PP) x True breeding White (pp) PP p p Copy the letters into the boxes – follow the arrows Pp pP Pp pP Shows the possible genotypes of the offspring All are Pp Shows the phenotype. How will the offspring look? All are purple

26. Probability and Punnett Squares Probability- the likelihood that a particular event will occur Example: A coin toss. There is a 50% chance each time that the coin will land heads up or tails up.

27. If out of 100 coin flips the coin always landed on heads, is there a greater probability it will land on heads on coin toss 101? No, it is still a 50% chance Past outcomes do not affect future coin flips. Coin Toss

28. We use probability to predict the outcome of genetic crosses in our Punnett Square If an organism has two different alleles for a trait, like Aa when sex cells are produced it will be random (like a coin toss) which allele ends up in each cell Heterozygous parents will make 2 types of sperm and egg. Ee

29. Punnett Squares give predicted ratios. Probabilities predict the average outcome of a large number of events. In genetics, the Larger the number of offspring, the closer the resulting numbers will get to expected values. –If parents only have 3-4 offspring it may not match Mendelian ratios.

30. Probability Example Aa x Aa If both of the parents are heterozygous Solve the Punnett Square Calculate the ratios Genotype Ratio 1AA:2Aa:aa Phenotype ratios 3 dominant : 1 recessive This tells us that the PROBABILITY of getting the dominant trait is 75% and only 25% chance of getting the recessive trait. Could all of the offspring be recessive? Is it likely?

31. Honors Principle of Independent Assortment Alleles for one trait segregate independently of those for another trait Genes that segregate independently do not influence each other’s inheritance A dihybrid cross shows this

32. HONORS DIHYBRID CROSS – cross of parentals with two different characteristics Do not get only round- yellow and wrinkled- green

33. Test Cross (Honors ONLY) Used to test the genotype of an F1 individual showing the dominant trait. F1 individuals are crossed back to a parent that is homozygous recessive. If any recessive offspring result from this cross, then the dominant individual is known to be a hybrid.

34. Beyond Dominant and Recessive Alleles Exceptions to the rules –Incomplete Dominance –Codominance –Multiple alleles –Polygenic traits

35. Incomplete Dominance One allele is not completely dominant over another –The Heterozygous shows an entirely different phenotype Red x White Produce Pink Cross of pink “brings back” red and white flowers

36. Incomplete Dominance examples Humans – Sickle cell disease (S) SS – have the disease ss – no disease Ss – mild version of disease, but resistant to malaria –Andalusian Fowl –A cross of black and white gives a blue/gray color black is dominant over white.

37. How these genotypes are written

38. Codominance Both alleles contribute to the phenotype In the heterozygous, both alleles are expressed Example – Blood type AB people who have the alleles A and B express both in their blood group.

39. Codominance Example Roan cows White cow crossed with a red bull = a cow that is roan, has both red and white hairs.

40. Multiple Alleles Genes that have more than two alleles –An individual won’t inherit more than 2 alleles, there are more than 2 possible alleles that exist in a population for that gene. Example: The ABO blood groups in humans

41. Human Genetic: Traits Human Blood Groups – an example of multiple alleles (3 or more) that show codominance (neither is dominant or recessive) 4 blood types: A, B, AB, O

42. How these Genotypes are written Universal donor Universal recipient

43. O positive is the most common blood type. Not all ethnic groups have the same mix of these blood types. Hispanic people, for example, have a relatively high number of O’s, while Asian people have a relatively high number of B’s. The mix of the different blood types in the U.S. population is: CaucasiansAfrican American HispanicAsian O +37%47%53%39% O -8%4% 1% A +33%24%29%27% A -7%2% 0.5 % B +9%18%9%25% B -2%1% 0.4 % AB +3%4%2%7% AB -1%0.3%0.2%0.1 % http://www.redcrossblood.org/learn-about-blood/blood-types

44. Human blood groups Rh Factors (-) and (+) have to have 2 negative alleles to be Rh – - only need one positive allele to be Rh + + - or + + Rh (-) blood types can only receive Rh(-) blood. Rh (+) can receive either Again, Rh factors are antigens on the red blood cells. People who are Rh- do not produce these antigens.

45. Problems What offspring would a man with type A blood and a woman with type B blood have? –Always assume AO and BO for A or B blood. Woman with blood type AB and a man with type O blood?

46. More problems…. A woman has type A blood Her child is type AB blood Could a man with type B blood be the baby daddy? Could a man with type O blood be the babies father? Explain.

47. Polygenic Traits Traits controlled by two or more genes An additive effect of two or more genes on a single phenotype.  AaBbCc aabbcc Aabbcc AaBbccAaBbCcAABbCc AABBCcAABBCC 20 ⁄ 64 15 ⁄ 64 6 ⁄ 64 1 ⁄ 64 Fraction of progeny

48. Polygenic Traits Traits controlled by two or more genes –Example – Skin Color –Example – Height –Eye color

49. Sex-Linked Inheritance Human Heredity A human karyotype –Picture of a person’s chromosomes

50. What does it tell us? 1) Humans have 46 chromosomes 2) 23 from each parent 3) The x and y chromosomes are sex chromosomes. They determine a persons sex. 4) The other 44 chromosomes are autosomes (any chromosome that is not a sex chromosome) Sex chromosomes

51. Sex-linked Genes Inheritance associated with the sex chromosomes –Many genes are found on the X chromosome –The Y chromosome is much smaller and carries only a few genes

52. Sex-linked Inheritance Sex-linked disorders (carried on the X chromosome) can be recessive or dominant Because males have just one X chromosome they will express the trait even if it is recessive. Females have 2 X chromosomes, so in order for them to express a recessive trait they must get two copies of the recessive allele.

53. Examples of sex-linked disorders Colorblindness An inability to distinguish certain colors –Red-green colorblindness is found in about 1 in 10 males. –In females it is rare - only about 1 in 100 has colorblindess Why? It is recessive, and a female would have to get 2 copies of the allele to express the trait. no such thing as color- what its like to be colorblind - youtube

54. Sex linked Genotypes Sex linked problem Cross a normal male with a female who is a carrier for hemophilia. Must always include the sex chromosomes Note: NEVER put alleles on the Y chromosome!!

55. Other examples of sex-linked traits Duchenne Muscular Dystrophy (DMD) –Rapid progressive weakening and loss of skeletal muscle early in life. –Most die by age 30 (some have lived into their 40’s and 50’s) –Affects 1 in 3,500 males Hemophilia –Blood does not clot properly –Affects about 1 in 5,000 to 1 in 25,000 males depending on the type of hemophilia. –Woman rarely suffer from severe hemophilia, but carries can have bleeding problems.

56. Genetics and the Environment Inherited traits are not solely determined by our genes. Environmental factors also influence our inherited characteristics –Example heart disease You may inherit a gene that makes you more likely to develop heart disease, but how you live your life, food you eat, exercise, will have an effect on whether you develop the disease or not.

57. Pedigree Charts A chart which shows the inheritance of genetic disorders. Based on phenotypes. Squares represent Males Circles represent Females Horizontal lines represent a marriage Vertical lines represent parents and their children A shaded square or circle indicates that a person expresses the trait.

58. Pedigree Problem Problem Solving p.343 http://www.npr.org/2012/02/27/147508790/am-i-my-genes-fate-family-and-genetic-testing Interview with Dr. about genetic testing and what problems that holds for families.

59. Eye color – not on test just info. The colored part of the eye is called the iris, which has pigmentation that determines our eye color.eyeiris Human eye color originates with three genes, two of which are well understood. These genes account for the most common colors — green, brown, and blue. Other colors, such as gray, hazel and multiple combinations are not fully understood or explainable at this time. Children can have completely different eye colors than either of their parents. But if both parents have brown eyes, it's most likely that their children also will have brown eyes. The darker colors tend to dominate, so brown tends to win out over green, and green tends to win out over blue. The iris is a muscle that expands and contracts to control pupil size. The pupil enlarges in dimmer lighting and grows smaller in brighter lighting. The pupil also shrinks when you focus on near objects, such as a book you are reading.pupil When the pupil size changes, the pigments in the iris compress or spread apart, changing the eye color a bit. Certain emotions can change both the pupil size and the iris color. That's why some people say their eyes change colors when they're angry or loving. Eye color also can change with age. This happens in 10 to 15 percent of the Caucasian population (people who generally have lighter eye colors).

60. Eye color not on test, just info. Heterochromia iridium (two different-colored eyes within a single individual) and heterochromia iridis (a variety of color within a single iris) are relatively rare in humans and result from increased or decreased pigmentation of the iris. Most cases are isolated and sporadic, conceivably resulting from an alteration in the expression of the above-mentioned genes (and those we have yet to find) within the cells of the entire iris or even a particular section.

61. What do you Know? 1. Long eyelashes (E) short eyelashes (e) –Show a cross that would result in ALL of the offspring having long eyelashes. (there may be more than one correct answer) 2. White (A) yellow (a) if you have a yellow parent, what would be the genotype of the other parent that when crossed, would result in offspring that were 50% white and 50% yellow? Give the parents genotypes. (Draw a Punnett square if you need to check your answer)

62. What do you Know? 3. Dimples (D) no dimples (d) if a homozygous dominant person marries a person without dimples what will be the phenotypic ratio of their offspring? Show the cross and draw a Punnett square to solve. 4. Wrinkled seeds (A) smooth (a) give the genotypic and phenotypic ratios when two heterozygous parents are crossed.