1. Human Anatomy and Physiology II Oklahoma City Community College
Medical Genetics
Human Anatomy and Physiology II
Oklahoma City Community College
This is the presentation on Medical Genetics for Human Anatomy and Physiology II at Oklahoma City Community College.
Dennis Anderson

2. Mitosis Produces daughter cells with 46 chromosomes
Used in growth and repair
You should recall that mitosis is a version of the cell cycle that produces daughter cells with 46 chromosomes in humans. Mitosis is used for growth and repair.

3. Mitosis DNA is duplicated Doubled chromosomes form from duplicated DNA
Each cms has 2 identical chromatids
Chromatid
During mitosis DNA is duplicated. This DNA is used to form doubled chromosomes. Each chromosome has two identical chromatids. These doubled chromosomes will soon be split into single chromosomes.
Chromatid

4. Mitosis Metaphase Chromosomes line up in a single row.
The doubled chromosomes line up in a single row during metaphase of mitosis.

5. Chromosomes separate Each chromatid becomes a single chromosome
The doubled chromosomes are pulled apart. Each chromatid now becomes a single chromosome.

6. Meiosis Reduce the chromosome number to half that of body cells
Produce gametes
Egg
Sperm
The meiosis version of the cell cycle produces cells with half the chromosome number of body cells. Meiosis is used just to produce the egg and sperm cells. These gametes will have 23 chromosomes.

7. Meiosis Metaphase Chromosomes line up in a double row.
During metaphase of meiosis the chromosomes line up in a double row.

8. Chromosomes separate Each each daughter cell gets doubled chromosomes
The chromosomes separate. Each daughter cell receives doubled chromosomes. These cells will have twice the DNA they need.

9. Doubled Chromosomes Separate in Second Meiotic Division
A second meiotic division is needed to separate the doubled chromosomes into single chromosomes.

10. Mitosis Metaphase Meiosis Metaphase
An important difference between mitosis and meiosis is the way the chromosomes line up during metaphase. They are in a single file in mitosis and a double file in meiosis.

11. Double Filed Chromosomes
Daughter cells receive ONE of each cms pair
Daughter cells receive ONE allele for most traits
New combinations of alleles possible
Cms 1
Cms 2
Homologous chromosomes are paired together during metaphase. The two number one chromosomes are paired together, the two number two chromosomes are paired together and so on for all 23 pairs. *This arrangement will ensure that each daughter cell will receive ONE of each chromosome pair. *It also insures that daughter cells will receive ONE allele for most traits. *New combinations of alleles result from the random arrangement of the chromosomes in metaphase of meiosis. For example, the red chromosomes represent the chromosomes a person inherited from their mother. The blue chromosomes represent those inherited from a person’s father. When the person produces gametes in meiosis he or she will pass on chromosomes from their parents—the grandparents of the offspring. The offspring will receive one number one chromosome. It could be a copy of chromosome one from their grandfather or grandmother. The odds of the chromosomes lining in up in metaphase the same way two times are one in 70 million, million times!

12. Gene A unit of heredity that controls the development of one trait
Made of DNA
A gene is a unit of heredity that controls the development of one trait. Genes are made of DNA. There are about 30,000 genes in man.

13. Allele Member of a paired gene Represented by a single letter
One allele comes from each parent
Represented by a single letter
An allele is a member of a paired gene. Most genes are made of paired alleles. A person gets one allele from each parent. A single letter represents an allele.

14. Examples of Alleles DD = Dwarfism Dd = Dwarfism dd = Normal height
Normal height = d
DD = Dwarfism
Dd = Dwarfism
dd = Normal height
For example, the letter D is used to represent the allele for dwarfism. A small d is the allele for normal height. If a person has DD or Dd they will be inherit dwarfism. If a person has dd they will grow to a normal height. Click on the link to hear the dwarf band. (It works best in Internet Explorer)
Dwarf Band

15. Dominant & Recessive Alleles
Dominant alleles are expressed
Recessive alleles are not expressed in the presence of a dominant allele
Recessive alleles are only expressed if both recessive alleles are present
Alleles can be dominant or recessive. Dominant alleles are expressed over recessive alleles. Recessive alleles are not expressed in the presence of a dominant allele. Recessive alleles are only expressed if both recessive alleles are present.

16. Homozygous Both alleles alike AA or aa
Homozygous is having both alleles alike. AA or aa are homozygous.

17. Heterozygous Alleles are different Aa
Heterozygous is when the alleles are different. Aa is homozygous.

18. Genotype Genetic make up Represented by alleles
DD & Dd are genotypes for dwarfism
Genotype refers to the genetic makeup. Genotypes are represented by alleles. DD and Dd are genotypes for dwarfism.

19. Phenotype A trait Genotype determines the phenotype
Dwarfism is a phenotype
The term phenotype refers to a trait. A person’s genotype determines their phenotype. Dwarfism is a phenotype.

20. Codominant Two different alleles are both dominant
A = allele for type A blood
B = allele for type B blood
AB = results in type AB blood
Codominant is when two different alleles are both dominant. For example, A is the allele for type A blood. B is the allele for type B blood. If a person inherits both the A and the B allele they will have type AB blood.

21. Karyotype Picture of chromosomes from an individual
A karyotype is a picture of chromosomes from an individual.

22. Homologous Chromosomes
Chromosomes of the same pair
Karyotypes are usually arranged with homologous chromosomes paired together
Homologous chromosomes are chromosomes of the same pair. Karyotypes have homologous chromosomes paired together.

23. Mutation Change in a gene or chromosome Causes an abnormal trait
A mutation is a change in a gene or chromosome. It will cause an abnormal trait.

24. Agent that causes mutations
Mutagen
Agent that causes mutations
Cigarette smoke
Pesticides
X-rays
Ulatraviolet light
Nuclear radiation
A mutagen is an agent that causes mutations. There are numerous mutagens in cigarette smoke. Pesticides are mutagens. X-rays, ultraviolet light and nuclear radiation are also mutagens. Most mutagens are also carcinogens or cancer causing agents.

25. Homologous chromosomes line up in a double file in metaphase I of meiosis
Homologous chromosomes line up in a double file in metaphase I of meiosis as discussed before.

26. Homologous Pairs Separate
The homologous pairs separate in the first meiotic division. *Two daughter cells are produced. These cells have doubled chromosomes and must be divided again.

27. Four Gametes With Single Chromosomes
The second meiotic division produces four gametes with single chromosomes.

28. Fertilization
Gametes unite during fertilization. *Chromosomes from both gametes make up the zygote formed.

29. Nondisjunction
Sometimes one pair of chromosomes fails to separate during meiosis. This is called nondisjunction. How do you think this will affect the offspring?

30. Trisomy
A trisomy will result after fertilization. *The zygote will have three chromosomes for the chromosome pair that did not separate during meiosis.

31. Sex Chromosomes
Sex chromosomes are the X and y chromosomes. They determine the sex of an individual.

32. Sex Chromosomes Male have Xy Females have XX
Male gametes have either X or y
Females have XX
Female gametes have X
Males have Xy. Sperm cells with either have an X or a y. Females have XX. The egg will have one X chromosome.

33. Autosomes Chromosomes 1-22
The autosomes are all the chromosomes except the sex chromosomes. Chromosomes 1 through 22 are autosomes.

34. X-Linked Traits Alleles are on the X chromosome
Females have two alleles
Males have one allele
Only one X chromosome
X-linked traits have their alleles on the X chromosome. Females with two X chromosomes will have two alleles for an X-linked trait. Males only have one allele for an X-linked trait.

35. Normal Male
Here is the karyotype for a normal male. There are two copies of each of the 22 autosomes and the X and y chromosomes.

36. Normal Female
The female karyotype also has two copies of the 22 autosomes plus two X chromosomes.

37. Trisomy 21 Down Syndrome
This is a karyotype for a person with an abnormal number of chromosomes. The have three copies of chromosome 21 because of nondisjunction in of the parents.

38. Down Syndrome Large tongue Flat face Slanted eyes
Single crease across palm
Mental retardation
Some are not
People with Down syndrome have a large tongue which often causes them have an open mouth. Their face is flat and the eyes are slanted. The palm of the hand has a single crease. Some individuals with Down syndrome are retarded but others are not.

39. Maternal Age & Down Syndrome
This slide shows the correlation of Down syndrome with the age of the mother. Paternal age is also a factor but it is not as strongly correlated as the age of the mother.

40. Trisomy 18 Edward Syndrome
Trisomy 18 is also known as Edward syndrome.

41. Edward Syndrome Heart defects Displaced liver Low-set ears
Abnormal hands
Severe retardation
98% abort
Lifespan < 1 year
Characteristics of Edward syndrome include heart defects, displaced liver and low-set ears. The hands have an unusual shape as shown on this slide. These individuals have severe retardation. Most of them abort before they are born. Those few who are born have a lifespan of less than one year.

42. Trisomy 13 Patau Syndrome
Trisomy 13 or Patau syndrome is illustrated here.

43. Patau Syndrome Cleft lip and palate Extra fingers & toes Defects
polydactylism
Defects
Heart
Brain
Kidneys
Most abort
Live span < 1 month
A cleft lip and palate are present in this condition. If you count the fingers on this baby you will find there are six digits. Polydactylism refers to extra digits. Defects of the heart, brain and kidneys are also present in this condition. Most individuals with this condition abort. Those babies that do survive live less than one month. The baby in this picture was stillborn.

44. Klinefelter Syndrome
Klinefelter syndrome results from an abnormal number of sex chromosomes. People with Klinefelter syndrome have a y chromosome so they are males. Having an extra X will cause them to have some feminine traits.

45. Klinefelter Syndrome Breast development Small testes Sterile
Low intelligence
Not retarded
They may exhibit slight breast development. Small testes and sterility is another characteristic of Klinefelter syndrome. They often have lower intelligence but are not retarded. Click on the link for the Klinefelter website to read about people with this condition.
Klinefelter Website

46. Turner Syndrome
Having only one X chromosome causes Turner syndrome. These individuals are females.

47. Turner Syndrome Short Not go through pruberty Produce little estrogen
Sterile
Extra skin on neck
Girls with Turner syndrome are short and do not go through puberty. The reason they do not is because they produce little estrogen. It takes two X chromosomes to produce a normal amount of estrogen. Most individuals with Turner syndrome are sterile. An unusual characteristic is extra skin on the neck. The girl in this picture is 18, but has not gone through puberty.

48. Fetal Testing
An abnormal number of chromosomes can be detected before birth by fetal testing. One method is amniocentesis. In this procedure amniotic fluid is withdrawn from the uterus. Some of the fetal cells will be present in amniotic fluid. The amniotic fluid is cultured for several weeks to increase the number of fetal cells present. These cells are then used to make a karyotype of the baby to check for chromosome number. Another type of fetal testing is chorionic villus sampling. Chorionic villi of the placenta are sampled. A karyotype can be prepared the next day with this method since the cells are much more dense.

49. Sickle Cell Anemia RBCs sickle shaped Anemia Pain Stroke Leg ulcers
Jaundice
Gall stones
Spleen, kidneys & lungs
Sickle cell anemia is a disease in which the red blood cells have a sickle shape. Sickle cells do carry as much oxygen and often plug up small blood vessels. The lack of oxygen causes anemia. When the oxygen supply is reduced to a part of the body pain will result. A reduced supply of oxygen to the brain can cause a stroke. Leg ulcers are the result of poor circulation. Sickle cells have a shorter life span than normal RBCs. When they break down bilirubin is released. Excess bilirubin can cause jaundice and gall stones. The spleen, kidneys and lungs are damaged during sickle cell anemia.

50. Sickle Cell Anemia Recessive allele, s codes for hemoglobin S
Long rod-like molecules
Stretches RBC into sickle shape
Homozygous recessive, ss have sickle cell anemia
Heterozygous, Ss are carriers
Sickle cell anemia is a disease in which the red blood cells have a sickle shape. Sickle cells do carry as much oxygen and often plug up small blood vessels. The lack of oxygen causes anemia. When the oxygen supply is reduced to a part of the body pain will result. A reduced supply of oxygen to the brain can cause a stroke. Leg ulcers are the result of poor circulation. Sickle cells have a shorter life span than normal RBCs. When they break down bilirubin is released. Excess bilirubin can cause jaundice and gall stones. The spleen, kidneys and lungs are damaged during sickle cell anemia.

51. Hemophilia Blood clotting impaired Recessive allele, h
carried on X cms
X-linked recessive trait
More common in males
Hemophilia is a blood clotting disease. It is caused by a recessive allele on the X chromosome. Hemophilia is an X-linked recessive trait. It is more common in males than females.

52. Albinism Lack of pigment Skin Hair Eyes
Albinism is another recessive condition. Albinos are unable to produce pigment in their skin, hair and eyes.

53. a A Enzyme Amino Acids Melanin Pigment AA = Normal pigmentation
aa = Albino
Normal people are able to synthesize the pigment melanin from amino acids. This process requires an enzyme. *The A allele has the directions to make this enzyme. *The a allele has a mistake in the directions and cannot make the enzyme. *The AA genotype has two copies of the directions for making pigment. Aa has only one good copy of the directions for making pigment, but only one copy is needed. The aa genotype cannot make the enzyme.

54. PKU Disease Phenylalanine excess Mental retardation if untreated
PKU disease results from an excess of phenylalanine. Too much phenylalanine can cause retardation in children. Click on the link to read Molly’s story about having PKU disease.
Molly’s Story

55. p P Enzyme Phenylalanine Tyrosine PP = Normal Pp = Normal pp = PKU
People without PKU disease produce an enzyme that converts excess phenylalanine to tyrosine. *The P allele has the directions for making this enzyme. *The p allele cannot make the enzyme. The genotypes PP and Pp are normal because they can produce the enzyme. The genotype pp, is unable to make the enzyme to breakdown excess phenylalanine. This individual will have PKU disease.

56. A man & woman are both carriers (heterozygous) for albinism
A man & woman are both carriers (heterozygous) for albinism. What is the chance their children will inherit albinism?
A man and a woman are both carriers for albinism. What is the chance their children will inherit albinism?

57. AA = Normal pigmentation Aa = Normal pigmentation (carrier)
aa = Abino
Man = Aa
Woman = Aa A A
The man will produce sperm cells by meiosis. During this process the alleles will separate into different sperm cells. He can make two different kinds of sperm cells. One kind will have the A allele and the other the a allele. The same is true of the woman when she produces an egg. a a

58. A a A Aa AA
One way to determine every combination of the man’s sperm cells and woman’s eggs is to align them on a square. It is called a Punnent square. *Each box of the square will receive an allele from one sperm and one egg. *AA will go in the box in the upper left. *The next square will receive the A allele from the sperm and the a allele from the egg. *Filling in each box will give every possible combination of eggs and sperms from a given couple.* a Aa aa

59. AA Aa aa Genotypes Phenotypes Probability 1 AA, 2Aa, 1aa 3 Normal
1 Albino
Probability
There is a lot of information we can derive from the Punnent square. The possible genotypes of the couple’s offspring are 1AA, 2Aa and 1aa out of four. Phenotypes are 3 normal and 1 albino out of 4. The probability of albinism is 1 out of 4 or 25%.
25% for albinism

60. A man & woman are both carriers (heterozygous) for PKU disease
A man & woman are both carriers (heterozygous) for PKU disease. What is the chance their children will inherit PKU disease?
Can you solve this problem for PKU disease?

61. P PP Pp P PP = Normal Pp = Normal (carrier) pp = PKU disease p p pp
Set up the Punnent square as shown in this slide. *The letters in the boxes are these p

62. PP Pp pp Genotypes Phenotypes Probability 1 PP, 2Pp, 1pp 3 Normal
1 PKU disease
Probability
This slide illustrates the possible genotypes, phenotypes and probability for PKU in the couple’s offspring.
25% for PKU disease

63. A man with sickle cell anemia marries a woman who is a carrier
A man with sickle cell anemia marries a woman who is a carrier. What is the chance their children will inherit sickle cell anemia?
Can you solve this problem for sickle cell anemia?

64. S ss s Ss SS = Normal Ss = Normal (carrier) ss = Sickle Cell s s
The Punnent square will look like this. *The genotypes of the offspring are in the Punnent square. s

65. Genotypes ss Ss Phenotypes Probability 2 Ss, 2ss 2 Normal (carriers)
2 Sickle cell
Probability
Genotypes, phenotypes and probability are shown on this slide.
50% for Sickle cell

66. A man with heterozygous dwarfism marries a woman who has normal height
A man with heterozygous dwarfism marries a woman who has normal height. What is the chance their children will inherit dwarfism? Dwarfism is dominant.
Try this problem for dwarfism. See if you can work it before advancing to the next slide.

67. d D Dd dd DD = Dwarf Dd = Dwarf dd = Normal d d
The Punnent square will look like this. *Here is the completed Punnent square. d

68. Genotypes Dd Phenotypes dd Probability 2 Dd, 2dd 2 Normal 2 Dwarfs
Genotypes, phenotypes and the probability of dwarfism for this problem are illustrated on this slide.
50% for Dwarfism

69. X-linked Recessive Traits
Alleles are on the X chromosome
Inheritance pattern different in males and females
X-linked recessive traits have their alleles on the X chromosome. The inheritance pattern is different in males than females.

70. XH Xh = Normal Female (Carrier)
Xh Xh = Hemophilic Female
XHy = Normal Male
Xhy = Hemophiliac Male
If a woman has one h allele she will not have hemophilia because a dominant H will enable her to produce clotting factors. A woman would have to have two h alleles to inherit hemophilia. However, a male only needs one h allele to have hemophilia.

71. A man with hemophilia marries a normal woman who is not a carrier
A man with hemophilia marries a normal woman who is not a carrier. What is the chance their children will inherit hemophilia? Hemophilia is X-linked recessive.
Be sure you write the alleles for hemophilia on the X chromosome to solve this problem.

72. XH XH Xh XH Xh XH Xh XHy XHy XH XH = Normal Female
XH Xh = Normal Female (Carrier)
Xh Xh = Hemophilic Female
XHy = Normal Male
Xhy = Hemophiliac Male XH XH Xh
XH Xh
XH Xh
It is always a good idea to write down every possible genotype and their corresponding phenotypes before you try to solve a genetics problem. Here are the genotypes for this problem. ****
XHy y
XHy

73. XH Xh XH Xh XHy Genotypes Phenotypes y Probability 2 XH Xh, 2XHy
2 Carrier Females
2 Normal Males
Probability
Note that all the females are carriers and that none of males inherit hemophilia from their father.
O% for Hemophilia

74. A normal man marries a normal woman who is a carrier for hemophilia
A normal man marries a normal woman who is a carrier for hemophilia. What is the chance their children will inherit hemophilia?
See if you can work this problem before advancing to the next slide.

75. XH Xh XH XH XH XH Xh XHy Xhy XH XH = Normal Female
XH Xh = Normal Female (Carrier)
Xh Xh = Hemophilic Female
XHy = Normal Male
Xhy = Hemophiliac Male XH Xh XH
XH XH
XH Xh
XHy
Xhy
Your Punnent square should look like this. * y

76. XH Xh XH XH , XH Xh, XHy, Xhy XH XH XH XH Xh XHy Xhy Genotypes
Phenotypes
2 Normal Females
1 Normal Males
1 Male Hemophiliac
XHy y
Xhy
The chance for hemophilia in a girl for this problem is 0%. One of the two boxes for boys has hemophilia. Therefore the change of hemophilia is 50% if the child is a boy.
Probability
50% for Male Hemophilic
0% for Female Hemophilic

77. The End
This concludes the presentation on medical genetics.