1. Press the F5 button on your keyboard to start the tutorial.

2. Sex-Linked Inheritance Place your keyboard aside. You will navigate with the mouse. Start from beginning The Guzman Family The Jackson Family The Chang Family Chromosomes & Karyotypes Sex-linked Inheritance

3. Mendel discovered the basic patterns of heredity in the 1800s when he was breeding pea plants. BACKHOME Gregor Mendel

4. Mendel discovered the basic patterns of heredity in the 1800s when he was breeding pea plants. Remember that purple flowers were dominant to white flowers. BACKHOME Gregor Mendel DOMINANT recessive

5. Mendel discovered the basic patterns of heredity in the 1800s when he was breeding pea plants. Remember that purple flowers were dominant to white flowers. Cross a heterozygous purple flower with a homozygous recessive white flower. BACKHOME Gregor Mendel P p pp Which genotype goes inside this square? PP pp PpPp X X PpPp Which genotype goes inside this square? PP pp PpPp X X Which genotype goes inside this square? PP pp PpPp XX PpPp Which genotype goes inside this square? PP PpPp X X pp

6. Mendel discovered the basic patterns of heredity in the 1800s when he was breeding pea plants. Remember that purple flowers were dominant to white flowers. Cross a heterozygous purple flower with a homozygous recessive white flower. What is the probability of growing purple flowered plants? BACKHOME Gregor Mendel P p p p PpPp pp PpPp 0% 25% 50% 75% 100% correct

7. Mendel discovered the basic patterns of heredity in the 1800s when he was breeding pea plants. Remember that purple flowers were dominant to white flowers. Cross a heterozygous purple flower with a homozygous recessive white flower. What is the probability of growing homozygous dominant plants? BACKHOME Gregor Mendel P p p p PpPp pp PpPp 0% 25% 50% 75% 100% correct

8. Mendel published his work in 1866. Even though his work is still very useful, it does have some limitations. Since 1866, scientists have been busy! As great as Mendel's work was, can we determine the gender of an individual using Mendel's work? BACKHOME Gregor Mendel Limitations? What limitations? NoYes Correct. My work cannot predict offspring gender. But my work was the foundation for others. X

9. In humans, there are 23 pairs of chromosomes (46 total). Karyotypes show an individual's chromosomes. The final pair of chromosomes allows us to determine the sex of the individual. Click on the karyotype above to reveal the sex of the individual used to create this karyotype. BACKHOME Chromosomes and Karyotypes This karyotype shows a girl. Let me teach you how.

10. So how do we know which is a female or male karyotype? Find chromosome pair #23. Like any pair of chromosomes, #23 comes in pairs (one from each parent). If the two chromosomes are equal sized, the individual has the XX chromosome combination and would be female. If the two chromosomes of #23 are different sized, the individual has the XY chromosome combination and would be male. Click on the female sex chromosomes in the above karyotype. BACKHOME Chromosomes and Karyotypes

11. Click on the male karyotype. BACKHOME Chromosomes and Karyotypes correct

12. Knowing that mom has the XX combination and dad has the XY combination, can we determine the probability of this couple having a boy or girl? Use the sex chromosomes (as a genotype) and fill in the Punnett square just like you would perform a genetics problem. BACKHOME Sex Determination

13. BACKHOME Sex Determination What is the probability of the child being born as a boy? 0%25%50%75%100% correct

14. BACKHOME Sex-Linked Inheritance Some traits and genes are found on the X or Y chromosome. These traits are called sex-linked. This means that not only can we predict whether or not a person will be healthy, but we also can predict whether the individual will be a boy or girl. X chromosome Y chromosome

15. BACKHOME Sex-Linked Inheritance Some traits and genes are found on the X or Y chromosome. These traits are called sex-linked. This means that not only can we predict whether or not a person will be healthy, but we also can predict whether the individual will be a boy or girl. Examples of sex-linked traits are: Hemophilia, Here is a normal vein. Click the vein to continue.

16. BACKHOME Sex-Linked Inheritance Some traits and genes are found on the X or Y chromosome. These traits are called sex-linked. This means that not only can we predict whether or not a person will be healthy, but we also can predict whether the individual will be a boy or girl. Examples of sex-linked traits are: Hemophilia, When cut, bleeding can occur. Click the vein to continue.

17. BACKHOME Sex-Linked Inheritance Some traits and genes are found on the X or Y chromosome. These traits are called sex-linked. This means that not only can we predict whether or not a person will be healthy, but we also can predict whether the individual will be a boy or girl. Examples of sex-linked traits are: Hemophilia, A blood clot forms to stop the bleeding. Click the vein to continue.

18. BACKHOME Sex-Linked Inheritance Some traits and genes are found on the X or Y chromosome. These traits are called sex-linked. This means that not only can we predict whether or not a person will be healthy, but we also can predict whether the individual will be a boy or girl. Examples of sex-linked traits are: Hemophilia, In hemophilia however, the clot is very weak and doesn’t stop the bleeding. This disease is caused by a recessive gene on the X chromosome. Click the vein to continue.

19. BACKHOME Sex-Linked Inheritance Some traits and genes are found on the X or Y chromosome. These traits are called sex-linked. This means that not only can we predict whether or not a person will be healthy, but we also can predict whether the individual will be a boy or girl. Examples of sex-linked traits are: Hemophilia, colorblindness, Here is a rainbow flag as seen by most people with normal vision. Click the flag to continue.

20. BACKHOME Sex-Linked Inheritance Some traits and genes are found on the X or Y chromosome. These traits are called sex-linked. This means that not only can we predict whether or not a person will be healthy, but we also can predict whether the individual will be a boy or girl. Examples of sex-linked traits are: Hemophilia, colorblindness, Here is the same flag as seen by many people who are color blind. Click the flag to continue.

21. BACKHOME Sex-Linked Inheritance Some traits and genes are found on the X or Y chromosome. These traits are called sex-linked. This means that not only can we predict whether or not a person will be healthy, but we also can predict whether the individual will be a boy or girl. Examples of sex-linked traits are: Hemophilia, colorblindness, and muscular dystrophy. Over time, the muscles begin to weaken and slowly waste away. Click the weaker bicep muscle to continue.

22. BACKHOME Sex-Linked Inheritance Some traits and genes are found on the X or Y chromosome. These traits are called sex-linked. This means that not only can we predict whether or not a person will be healthy, but we also can predict whether the individual will be a boy or girl. Examples of sex-linked traits are: Hemophilia, colorblindness, and muscular dystrophy. As the muscles weaken, often the sufferer becomes wheelchair bound for the rest of their life. Average life span is only about 25 years.

23. BACKHOME Sex-Linked Punnett Squares Since the genes that cause these disorders are usually found on the X chromosome, we will use the letters XH XH to abbreviate a dominant healthy allele on the X chromosome.

24. BACKHOME Sex-Linked Punnett Squares Since the genes that cause these disorders are usually found on the X chromosome, we will use the letters X H to abbreviate a dominant healthy allele on the X chromosome. Key for this tutorial: XH XH = Dominant healthy

25. BACKHOME Sex-Linked Punnett Squares Since the genes that cause these disorders are usually found on the X chromosome, we will use the letters XH XH to abbreviate a dominant healthy allele on the X chromosome. Therefore Xh Xh will be used to abbreviate a recessive unhealthy allele on the X chromosome. Key for this tutorial: X H = Dominant healthy

26. BACKHOME Sex-Linked Punnett Squares Since the genes that cause these disorders are usually found on the X chromosome, we will use the letters X H to abbreviate a dominant healthy allele on the X chromosome. Therefore X h will be used to abbreviate a recessive unhealthy allele on the X chromosome. Key for this tutorial: X H = Dominant healthy Xh Xh = recessive disease

27. BACKHOME Sex-Linked Punnett Squares Since the genes that cause these disorders are usually found on the X chromosome, we will use the letters XH XH to abbreviate a dominant healthy allele on the X chromosome. Therefore Xh Xh will be used to abbreviate a recessive unhealthy allele on the X chromosome. Since most sex-linked disorders are found on the X chromosome, this tutorial will not address Y-linked problems. Key for this tutorial: X H = Dominant healthy X h = recessive disease

28. BACKHOME Men? Women? Both? Men only have two possible chromosome combinations. If guys are healthy, they must be X H Y. Key for this tutorial: X H = Dominant healthy X h = recessive disease

29. BACKHOME Men? Women? Both? Men only have two possible chromosome combinations. If guys are healthy, they must be X H Y. Key for this tutorial: X H = Dominant healthy X h = recessive disease X H Y = healthy

30. BACKHOME Men? Women? Both? Men only have two possible chromosome combinations. If guys are healthy, they must be X H Y. If a guy has a sex-linked disease, he must be X h Y. Key for this tutorial: X H = Dominant healthy X h = recessive disease X H Y = healthy

31. BACKHOME Men? Women? Both? Men only have two possible chromosome combinations. If guys are healthy, they must be X H Y. If a guy has a sex-linked disease, he must be X h Y. Key for this tutorial: X H = Dominant healthy X h = recessive disease X H Y = healthy X h Y = disease

32. BACKHOME Men? Women? Both? Sex-linked disorders are most commonly found on the X chromosome. They are also more common in males because males only have 1 X chromosome. If a male’s only X chromosome is damaged, males do not have a “backup” X chromosome. Key for this tutorial: X H = Dominant healthy X h = recessive disease X H Y = healthy X h Y = disease

33. BACKHOME Men? Women? Both? Sex-linked disorders are most commonly found on the X chromosome. They are also more common in males because males only have 1 X chromosome. If a male’s only X chromosome is damaged, males do not have a “backup” X chromosome. Key for this tutorial: X H = Dominant healthy X h = recessive disease X H Y = healthy X h Y = disease What about my Y chromosome? If my Y chromosome is “healthy” and my X chromosome has a “disease”, will I be healthy? YesNo

34. BACKHOME Men? Women? Both? Key for this tutorial: X H = Dominant healthy X h = recessive disease X H Y = healthy X h Y = disease What about my Y chromosome? If my Y chromosome is “healthy” and my X chromosome has a “disease”, will I be healthy? Actually, no. These disorders are mostly found on the X chromosome. So even though you may have a normal Y chromosome, it won’t protect you from these disorders.

35. BACKHOME Men? Women? Both? But what about women? Women don’t have a Y chromosome. Women have two X chromosomes. Key for this tutorial: X H = Dominant healthy X h = recessive disease X H Y = healthy X h Y = disease What about my Y chromosome? If my Y chromosome is “healthy” and my X chromosome has a “disease”, will I be healthy? No correct

36. BACKHOME Men? Women? Both? Women could have 1 of 3 different combination of X chromosomes. Key for this tutorial: X H = Dominant healthy X h = recessive disease

37. BACKHOME Men? Women? Both? If both her X chromosomes have healthy alleles, she will be healthy. Key for this tutorial: X H = Dominant healthy X h = recessive disease X H X H = healthy

38. BACKHOME Men? Women? Both? If both her X chromosomes have the allele for disease, she will have a disease. Key for this tutorial: X H = Dominant healthy X h = recessive disease X h X h = disease X H X H = healthy

39. BACKHOME Men? Women? Both? But if she is heterozygous, she will be healthy. Women have a “backup” X chromosome in case their other has a recessive disease. This is the reason why sex-linked diseases in women is very rare. Men don’t have this advantage. Girl Power! Key for this tutorial: X H = Dominant healthy X h = recessive disease X H X H = healthy X H X h = healthy (carrier) X h X h = disease

40. BACKHOME Three Families Here are three families. Each of them has a history of a sex-linked disorder. They need your help because they hope to have children in the near future. Click the Guzman Family to start. The Jackson FamilyThe Guzman Family The Chang Family

41. BACKHOME The Guzman Family Hemophilia is a sex-linked recessive disorder found on the X chromosome. Sufferers of hemophilia lack a protein that helps their blood coagulate (clot) when injured. Thus, the person can lose a lot of blood from very minor injuries. Click on the vein to continue.

42. BACKHOME The Guzman Family Hemophilia is a sex-linked recessive disorder found on the X chromosome. Sufferers of hemophilia lack a protein that helps their blood coagulate (clot) when injured. Thus, the person can lose a lot of blood from very minor injuries. Mr. Guzman is a hemophiliac. What is his genotype? X H YX h Y Correct. He does not have a “backup” X chromosome. The capital H would mean he would be healthy. But the story says he is a hemophiliac.

43. BACKHOME The Guzman Family Hemophilia is a sex-linked recessive disorder found on the X chromosome. Sufferers of hemophilia lack a protein that helps their blood coagulate (clot) when injured. Thus, the person can lose a lot of blood from very minor injuries. Mrs. Guzman is healthy with no family history of hemophilia. What is her genotype? X H X H X H X h X h X h Mr. Guzman’s Genotype: X h Y Capital H is healthy. Lowercase h is the disease. If she was X h X h, then she would have the disease. She has “no history of hemophilia” in her family. If she has a X h that would mean it runs in her family. Correct. She must be homozygous dominant.

44. BACKHOME The Guzman Family So lets fill in the Punnett square below. Ladies first. XhXh Y XHXH XHXH

45. BACKHOME The Guzman Family Now it’s Mr. Guzman’s turn. XhXh Y XHXH XHXH XHXH XHXH

46. BACKHOME The Guzman Family Now it’s Mr. Guzman’s turn. XhXh Y XHXH XHXH XHXH XHXH XhXh Y continue

47. BACKHOME The Guzman Family Now it’s Mr. Guzman’s turn. XhXh Y XHXH XHXH XHXH XHXH XhXh Y

48. BACKHOME The Guzman Family Now it’s Mr. Guzman’s turn. XhXh Y XHXH XHXH XHXH XhXh XHXH XHXH XhXh Y

49. BACKHOME The Guzman Family Now it’s Mr. Guzman’s turn. XhXh Y XHXH XHXH XHXH XHXH XhXh Y XHXH XHXH XhXh Y

50. BACKHOME The Guzman Family Now it’s Mr. Guzman’s turn. XhXh Y XHXH XHXH XHXH XHXH XHXH XhXh XhXh Y XHXH XHXH XhXh Y

51. BACKHOME The Guzman Family Now it’s Mr. Guzman’s turn. XhXh Y XHXH XHXH XHXH XHXH XHXH XHXH XhXh XhXh Y Y XHXH XHXH XhXh Y There are 2 squares that show a healthy boy. Click on each of them. Healthy boy

52. BACKHOME The Guzman Family What is the probability of having a child, boy or girl, with hemophilia? XhXh Y XHXH XHXH XHXH XHXH XHXH XHXH XhXh XhXh Y Y XHXH XHXH XhXh Y 0% 25%50%75%100% I have good news. Even though Mr. Guzman has hemophilia, none of your children will be hemophiliacs. But there is something to worry about… If you have daughters, they will be carriers of hemophilia. They can pass the gene to their children.

53. BACKHOME The Guzman Family Thank you very much for your help doctor.

54. BACKHOME The Guzman Family This information helps to ease the stress of starting a family.

55. BACKHOME The Guzman Family You’re so very welcome. Please excuse me. I have another family to meet with.

56. BACKHOME The Jackson Family Colorblindness is a sex-linked recessive disorder found on the X chromosome. Colorblindness is the inability to perceive differences between some of the colors that other people can distinguish. Normal vision Colorblindness

57. BACKHOME The Jackson Family Colorblindness is a sex-linked recessive disorder found on the X chromosome. Colorblindness is the inability to perceive differences between some of the colors that other people can distinguish. Remember that women have two X chromosomes. Because the disorder is recessive, a woman needs two recessive alleles to inherit the disorder. The Jackson Family

58. BACKHOME The Jackson Family Colorblindness is a sex-linked recessive disorder found on the X chromosome. Colorblindness is the inability to perceive differences between some of the colors that other people can distinguish. Remember that women have two X chromosomes. Because the disorder is recessive, a woman needs two recessive alleles to inherit the disorder. Mr. Jackson is colorblind. What is his genotype? X H YX h Y Correct. He does not have a “backup” X chromosome. Mr. Jackson is colorblind and that’s recessive. Recessive letters are lowercase. The Jackson Family

59. BACKHOME The Jackson Family Colorblindness is a sex-linked recessive disorder found on the X chromosome. Colorblindness is the inability to perceive differences between some of the colors that other people can distinguish. Remember that women have two X chromosomes. Because the disorder is recessive, a woman needs two recessive alleles to inherit the disorder. Mrs. Jackson has normal vision, but her father was colorblind. Therefore her father passed her a copy of the colorblind allele. What is her genotype? Mr. Guzman’s Genotype: X h Y X H X H X H X h X h X h If she was this, she would be colorblind. But her father was colorblind and would pass his X h to her correct The Jackson Family

60. BACKHOME The Jackson Family So let’s complete their Punnett square. XhXh YXHXH XhXh XhXh YXHXH XhXh

61. BACKHOME The Jackson Family So let’s complete their Punnett square. XhXh YXHXH XhXh XhXh Y XHXH XhXh Which genotype goes inside this square? XHXHXHXH XHYXHY XhYXhY XHXhXHXh XhXhXhXh

62. BACKHOME The Jackson Family So let’s complete their Punnett square. XhXh YXHXH XhXh XhXh Y XHXH XhXh XHXhXHXh Which genotype goes inside this square? XHXHXHXH XHYXHYXhYXhYXHXhXHXh XhXhXhXh

63. BACKHOME The Jackson Family So let’s complete their Punnett square. XhXh YXHXH XhXh XhXh Y XHXH XhXh XHXhXHXh Which genotypegoes inside thissquare? XHXHXHXH XHYXHY XhYXhY XHXhXHXh XhXhXhXh XhXhXhXh

64. BACKHOME The Jackson Family So let’s complete their Punnett square. XhXh YXHXH XhXh XhXh Y XHXH XhXh XHXhXHXh Which genotypegoes inside thissquare? XHXHXHXH XHYXHY XhYXhY XHXhXHXh XhXhXhXh XhXhXhXh XHYXHY

65. BACKHOME The Jackson Family Great job. Now let’s analyze the Punnett square. Click on the genotype of a colorblind girl. XhXh YXHXH XhXh XhXh Y XHXH XhXh XHXhXHXh XhXhXhXh XHYXHYXhYXhY Colorblind girl Normal vision girl Normal vision boy Colorblind boy correct

66. BACKHOME The Jackson Family What is the probability of having a child (boy or girl) with normal vision? XhXh YXHXH XhXh XhXh Y XHXH XhXh XHXhXHXh XhXhXhXh XHYXHYXhYXhY correct 0% 25%50%75%100% Normal vision

67. BACKHOME The Jackson Family Even if your children are colorblind, there’s really nothing to worry about. There’s no negative health effects.

68. BACKHOME The Jackson Family I may be colorblind, but I can see my beautiful wife. Thank you doctor.

69. BACKHOME The Chang Family Muscular Dystrophy is a sex-linked recessive disorder found on the X chromosome. The muscles of sufferers begin to deteriorate at an early age leaving the individual weakened and largely immobile. Death by mid-20s is common.

70. BACKHOME The Chang Family Muscular Dystrophy is a sex-linked recessive disorder found on the X chromosome. The muscles of sufferers begin to deteriorate at an early age leaving the individual weakened and largely immobile. Death by mid-20s is common. Mrs. Chang has a history of muscular dystrophy in her family and as a result they are considering adoption as an alternative. Because the disorder is recessive, a woman needs two recessive genes to inherit the disorder. Can you help?

71. BACKHOME The Chang Family Muscular Dystrophy is a sex-linked recessive disorder found on the X chromosome. The muscles of sufferers begin to deteriorate at an early age leaving the individual weakened and largely immobile. Death by mid-20s is common. Mrs. Chang has a history of muscular dystrophy in her family and as a result they are considering adoption as an alternative. Because the disorder is recessive, a woman needs two recessive genes to inherit the disorder. Can you help? Mr. Chang is healthy with no history of muscular dystrophy. What is his genotype? X H YX h Y The story says Mr. Chang is healthy. If he was X h Y he would have the disease. Correct. X H means he would be healthy.

72. BACKHOME The Chang Family Mr. Chang X H Y Muscular Dystrophy is a sex-linked recessive disorder found on the X chromosome. The muscles of sufferers begin to deteriorate at an early age leaving the individual weakened and largely immobile. Death by mid-20s is common. Mrs. Chang has a history of muscular dystrophy in her family and as a result they are considering adoption as an alternative. Because the disorder is recessive, a woman needs two recessive genes to inherit the disorder. Can you help? Mrs. Chang is healthy even though she carries the recessive allele for muscular dystrophy. What is her genotype? X H X H X H X h X h X h If she was this, she wouldn’t be healthy. The story says she is a “carrier” correct

73. BACKHOME The Chang Family Mr. Chang X H Y Lets complete their Punnett Square. Mrs. Chang X H X h Mrs. Chang

74. BACKHOME The Chang Family Mr. Chang X H Y Lets complete their Punnett Square. Mrs. Chang X H X h XHXH XhXh Mr. Chang

75. BACKHOME The Chang Family Mr. Chang X H Y Lets complete their Punnett Square. Mrs. Chang X H X h XHXH Y XHXH XhXh

76. BACKHOME The Chang Family Mr. Chang X H Y Lets complete their Punnett Square. Mrs. Chang X H X h XHXH Y XHXH XhXh XHXH XHXH

77. BACKHOME The Chang Family Mr. Chang X H Y Lets complete their Punnett Square. Mrs. Chang X H X h XHXH Y XHXH XhXh XHXH XHXH XHXH XhXh

78. BACKHOME The Chang Family Mr. Chang X H Y Lets complete their Punnett Square. Mrs. Chang X H X h XHXH Y XHXH XhXh XHXH XHXH XHXH Y XHXH XhXh

79. BACKHOME The Chang Family Mr. Chang X H Y Mrs. Chang X H X h XHXH Y XHXH XhXh XHXH XHXH XHXH Y XhXh Y XHXH XhXh What is the probability the Chang’s have a child with muscular dystrophy? correct 0% 50%25%75%100%

80. BACKHOME The Chang Family Mr. Chang X H Y Mrs. Chang X H X h XHXH Y XHXH XhXh XHXH XHXH XHXH Y XhXh Y XHXH XhXh Click the square below that would lead to a child with muscular dystrophy. Muscular dystrophy correct

81. BACKHOME The Chang Family XHXH Y XHXH XhXh XHXH XHXH XHXH Y XhXh Y XHXH XhXh You have an important decision to make. Muscular dystrophy

82. BACKHOME The Chang Family XHXH Y XHXH XhXh XHXH XHXH XHXH Y XhXh Y XHXH XhXh You have a 25% of having a boy inherit this disease. Muscular dystrophy

83. BACKHOME The Chang Family XHXH Y XHXH XhXh XHXH XHXH XHXH Y XhXh Y XHXH XhXh If that happens, he will not likely live past his 20’s. Muscular dystrophy

84. BACKHOME The Chang Family XHXH Y XHXH XhXh XHXH XHXH XHXH Y XhXh Y XHXH XhXh But there is a 75% chance that every child will be fine. Correct? Muscular dystrophy

85. BACKHOME The Chang Family XHXH Y XHXH XhXh XHXH XHXH XHXH Y XhXh Y XHXH XhXh That’s correct. However, I wanted you to know the probability. Muscular dystrophy

86. BACKHOME The Chang Family XHXH Y XHXH XhXh XHXH XHXH XHXH Y XhXh Y XHXH XhXh Thank you doctor. We will discuss this information and perhaps consider adoption. Muscular dystrophy

87. BACKHOME Conclusion This is different from my pea plant experiments. The genes to give pea plants their color and texture are not found on the sex chromosomes.

88. BACKHOME Conclusion It turns out that the pea plant characteristics I studied are found on nonsex chromosomes, or autosomes.

89. BACKHOME Conclusion Only genes and traits that can be found on the X or Y chromosome are called sex-linked.

90. BACKHOME Conclusion Most of these disorders are recessive, which means that women are less likely to suffer from the disorder because woman has a “backup” X chromosome.

91. The End BACKHOME End Tutorial