1. Incomplete Vs. Co-dominance
Codominance - A form of inheritance in which both alleles are equally shown.
Incomplete dominance - A form of inheritance in which the heterozygous alleles are both expressed, resulting in a combined phenotype.
Most commonly found in plants.
A red and a white allele gives pink. If it were codominance, you would see the red and white colors.

2. Test Cross Used to determine an organisms genotype.
Either Bb or BB
Always a dominant unknown mated with pure recessive
B? X bb

3. Human Genetics: Karyotypes
46 TOTAL
23 homologous pairs
46 TOTAL
Chromosomes
23 homologous pairs

4. What is the difference between an Autosome and a Sex-chromosome?
Autosomes are the first 22 homologous pairs of human chromosomes that do not influence the sex of an individual.
Sex Chromosomes are the 23rd pair of chromosomes that determine the sex of an individual.

5. Autosomal Traits
Genes located on Autosomes control Autosomal traits and disorders.
2 Types of Traits:
Autosomal Dominant
Autosomal Recessive

6. Autosomal Recessive Traits
In order to express the trait, two recessive alleles must be present.
What would be the genotype of an individual with an autosomal recessive trait? (A = dominant) aa
What would be the genotype of an individual without the autosomal recessive trait?
AA or Aa
Aa – called a Carrier because they carry the recessive allele and can pass it on to offspring, but they do not express the trait.

7. Albinism
Defect of melanin production that results in little or no color in the skin, hair, and eyes

8. Albinism

9. Albinism

10. How does it happen? Affected Genotype: aa

11. Cystic Fibrosis
Disease that causes the body to produce unusually thick, sticky mucus that:
Clogs the lungs and leads to lung infections
Obstructs the pancreas
Stops natural enzymes from helping the body break down and absorb food

12. How does it happen? Affected Genotype: cc

13. Red blood cells carry oxygen.
Sickle Cell Anemia
Caused by an abnormal hemoglobin shape which causes the red blood cells to have a crescent shape.
Red blood cells carry oxygen.

14. How does it happen? Affected Genotype: ss

15. Tay–Sachs disease Symptoms: Mainly occurs in Jewish people
a build up of lipids in the brain
Seizures
blindness
Mainly occurs in Jewish people

16. Tay-Sachs Disease

17. PKU (phenylketournia)
symptoms;
cannot break down the specific amino acid (phenylalanine found in foods like milk)
results in brain damage
Mainly occurs in people of European descent

18. Autosomal Dominant Traits
If dominant allele is present on the autosome, then the individual will express the trait.
What would be the genotype of an individual with an autosomal dominant trait?
AA and Aa (Heterozygotes are affected)
What would be the genotype of an individual without the autosomal dominant trait? aa

19. Huntington’s Disease
Causes the break down of brain cells, (neurons) in certain areas of the brain.
Causes uncontrolled movements, loss of intellectual faculties, and emotional disturbance.

22. How does it happen? Affected Genotype: HH or Hh

23. Progeria
Drastic premature aging, rare, die by age 13. Symptoms include limited growth, alopecia, small face and jaw, wrinkled skin, atherosclerosis, and cardiovascular problems but mental development not affected.

24. Sex-Linked Traits
Sex-linked traits are produced by genes only on the X chromosome.
They can be Dominant or Recessive.
What would be the genotypes of a male and female that have a Sex-linked Dominant trait and do not express the trait?
Expresses Trait: Male - XA Y Female - XA XA or XA Xa
No Expression: Male - Xa Y Female - Xa Xa
What would be the genotypes of a male and female that have a Sex-linked Recessive trait and do not express the trait?
Expresses Trait: Male - Xa Y Female - Xa Xa
No Expression: Male - XA Y Female - XA XA or XA Xa
(Carrier)
Most Sex-linked traits are Recessive!

25. Inability to see colors in the normal way
Color Blindness
Inability to see colors in the normal way

28. How does it happen? Affected Genotypes: XbXb XbY

29. Inability of the blood to clot properly
Hemophilia
Inability of the blood to clot properly

31. How does it happen? Affected Genotypes: XhXh XhY

32. Pedigree Analysis
A pedigree shows the relationship between parents and children over the generations and how a trait is passed down from one generation to the next.

33. How to Construct a Pedigree?
A Pedigree is a visual showing the pattern of inheritance for a trait. (Family tree)
Symbols and Rules:
Male = Female =
Affected = Unaffected = Carrier =
Link parents together with a line and then make a vertical line to connect to offspring.

34. Autosomal Dominant Pedigree
Draw a Pedigree showing a cross between Heterozygous parents that have 2 boys and 2 girls. (Show all possibilities)
Genotypes of Affected and Unaffected:
AA and Aa = Affected aa = Unaffected Aa AA aa

35. Autosomal Recessive Pedigree
Draw a Pedigree showing a cross between Heterozygous parents that have 2 boys and 2 girls. (Show all possibilities)
Genotypes of Affected and Unaffected:
AA=Unaffected Aa=Carrier, Unaffected aa=Affected Aa AA aa

36. Sex-Linked Recessive Pedigree
Draw a Pedigree showing a cross between a normal male and a Carrier Female.
Genotypes of Parents:
Male = Xh Y Female = XH Xh
XRY
XrY
XRXR
XRXr
XRXr

38. Characteristics of Autosomal Dominant, Autosomal Recessive, and Sex-linked Recessive Traits
In groups, analyze your notes on each type of disorder and examine the pedigrees.
Come up with rules/characteristics for each type of Trait.

40. Types of Pedigrees: Recessive
Affected Genotypes: bb
Unaffected Genotypes: BB or Bb
HINT: Recessive Disorders skip
generations

41. Is the Pedigree below showing Recessive Inheritance?

42. Recessive Inheritance?

43. Recessive Inheritance?

44. Types of Pedigrees: Sex-linked
Affected Genotypes:
XbXb or XbY
Unaffected Genotypes:
XBXB or XBXb and XBY
HINT: Mainly males are affected

45. Is the Pedigree below showing Sex-Linked Inheritance?

46. Sex-linked Inheritance?

47. Sex-linked Inheritance?

48. Types of Pedigrees: Dominant
Affected Genotypes: BB or Bb
Unaffected Genotypes: bb

49. Is the Pedigree below showing Dominant Inheritance?

50. Dominant Inheritance?

51. Dominant Inheritance?

52. What type of Inheritance? What is genotype of Individual I-1?
How many generations?
What type of Inheritance?
What is genotype of Individual I-1?

53. What type of Inheritance? What is genotype of Individual I-1?
How many generations?
What type of Inheritance?
What is genotype of Individual I-1?

54. Pedigrees and Genetic Disorders

55. Mutations Gene Mutations
1. Caused by a change in the amino acid sequence of a protein
2. Impacts of mutations: lethal, neutral, or beneficial
3. Gene mutation are caused by a change to one or more bases in nucleotide sequence of DNA
A. mutations are rare because cells have proofreading and correction enzymes
B. these chance events (mutations) are caused by mutagens
Ex. viruses, UV light, chemicals like mustard gas

56. Mutations Chromosomal Mutations
1. Caused by a change in structure or number of chromosomes
2. Detected by KARYOTYPING which matches homologous chromosomes in a diploid (2N) cell by:
Size of chromosome
Length of chromatid arms
3. Centromere location

57. Karyotype

58. Chromosomal Mutations
Structure
a. Deletion - loss of part of a chromosome AC  DEF
b. Duplication - segment is repeated ABBC  DEF
c. Inversion - orientation is reverse of normal AED  CBF (twisting)
d. Translocation - parts are broken off and added to another chromosome
Ex. ABC  DEF and GH  IJK is changed to ABC  JK and GH  IDEF

59. Chromosomal Mutations
Nondisjunction deals with whole chromosomes or sets of chromosomes "not coming apart.”
During meiosis a cell gets both copies of a chromosome and the other cell is missing one chromosome because sister chromatids didn’t separate
Monosomy is the condition of having only 1 chromosome of a homologous pair
Turner Syndrome= monosomy of 23rd pair
II. Trisomy is the condition of having 3 chromosomes of a homologous pair
Down syndrome (21st pair), Klinefelter Syndrome (23rd pair), XYY syndrome (23rd pair)

60. Down Syndrome

61. Cystic fibrosis Caused by a recessive allele; ff Symptoms:
organs produce a thick mucus causing congestion in the lungs
digestive tract problems
pneumonia like symptoms
Mainly occurs in Caucasians

62. Albinism Caused by a recessive allele; aa Symptoms:
no melanin in the skin
resulting in an albino:
white skin
pink to red eyes

63. Huntington disease Caused by a dominant allele; HH or Hh Symptoms:
breaks down the nervous system, fatal

64. Sickle Cell Anemia
Caused by a co-dominant allele (A’) which codes for abnormal hemoglobin
hemoglobin is found on the red blood cells and carries oxygen
Symptoms:
sickle shape red blood cells, clotting, extensive pain, can be fatal
Genotypes:
AA = normal
AA’ = normal but a carrier
A’A’ = diseased
Mainly African people

65. Color blindness
Sex-linked disorder caused by a recessive allele only found on the X sex chromosome:
XC XC = normal female; XC Xc= normal, but a carrier
Xc Xc= color blind female
XC Y = normal male; XcY = color blind male
Symptoms:
cannot distinguish red from green

66. Color Blindness

67. Hemophilia
Sex-linked disorder caused a recessive allele only found on the X sex chromosome
normal female = XH XH= normal, but a carrier XH Xh
hemophiliac female = XhXh
normal male = XHY; XhY = hemophiliac male
Symptoms:
excessive bleeding from a minor injury, fatal

68. Down syndrome (trisomy)
Cause by nondisjunction
too many chromosomes: 3 chromosomes for the 21st pair of homologous chromosomes; resulting in 47 total chromosomes
Symptoms:
Almond shape eyes
Enlarged tongues
Some can be mentally and physically challenged

69. Down syndrome (trisomy)

70. Klinefelter syndrome Cause by nondisjunction Symptoms:
too many chromosomes: 3 sex chromosomes = XXY; the sex is male; resulting in 47 total chromosomes
Symptoms:
Underdeveloped male sex organs
Sterility
May have feminine body parts

71. Turner Syndrome Cause by nondisjunction Symptoms:
not enough chromosomes; 1 sex chromosome = XO the sex is female; resulting in 45 total chromosomes
Symptoms:
Females are usually short
Sex organs may not develop
Sterility

72. Turner Syndrome

73. Pedigree Analysis
In a pedigree chart, certain shapes indicate gender and colors signify whether or not they carry the trait or show the trait
A circle represents a female.
A square represents a male.
A horizontal line between 2 people indicates marriage.
A vertical line extending from a marriage line indicates the offspring from the couple.
A solid shaded shape represents a person who shows the trait in their phenotype.
A half shaded shape represents a person who is a carrier of the trait but does not show the trait. NOTE: some pedigrees don’t indicate carriers

74. Pedigree Analysis

75. Pedigree Analysis
Generations are indicated with Roman numerals (I, II, III) and
individuals within generations are marked with arabic
numbers (1, 2, 3, 4).
Pedigree Questions: this pedigree doesn’t indicate carriers
1. What sex is individual I-2?
How many children are in the 2nd generation
from the union of I-1 and I-2?
3. What are their sexes?
4. Which individual was married in generation 2?
5. How many daughters are in generation 3?
6. How many sons are in generation 4?
List the 3 individuals who were afflicted with
sickle cell anemia?
8. Were individuals I-1 and I-2 carriers of sickle cell?
9. How do you know? (Explain your answer to #8)
10. List another carrier of sickle cell anemia.
= sickle cell anemia

76. Karyotype Practice
Down Syndrome Male

77. Karyotype Practice
Klinefelter Male

78. Turner Syndrome Female
Karyotype Practice
Turner Syndrome Female

79. Karyotype Practice
XYY Syndrome Male

80. Pedigrees and Genetic Disorders
Unit 9, Part 4 Notes
Pedigrees and Genetic Disorders

81. What does a pedigree look like?
What is a pedigree?
Definition: a graphic representation of genetic inheritance used by geneticists to map genetic traits
What does a pedigree look like?
Affected
Generations in separate rows indicated by Roman numerals (I, II, III…)
Individuals within one generation indicated by Arabic numerals (1, 2, 3…)
Parents connected by horizontal lines
Offspring connected by vertical lines
Female
Male
Carrier
Unaffected
Dead

82. Let’s look at an example… Tay Sachs disease
Occurs in people of Jewish descent
Enzyme that breaks down lipids in the brain is defective. Lipid buildup kills brain cells.
Always results in death, usually by age 5
Caused by a recessive allele
Let’s look at an example… Tay Sachs disease

83. Pedigree for Tay Sachs disease
Carrier
Carrier

84. Huntington’s Disease Caused by a rare dominant allele
Doesn’t show up till age 30-50
Breaks down areas of the brain, loss of control of all body functions
No treatment
Huntington’s Disease

85. Pedigree for Huntington’s Disease
normal
carrier

86. What if the trait is sex-linked? How can you tell?
Answer: Most affected individuals are males

87. Let’s try one…Is this sex-linked or not?
Answer: Yes

88. More practice with pedigrees…
Interactive pedigree activity
Pedigree quiz
Punnett Square and Pedigree problems

89. Sex Chromosomes 2 sex chromosomes Typical Female = XX
Typical Male = XY

90. Autosomes: Any chromosome that’s not a sex chromosome
22 pairs of Autosomes

91. Autosomal Recessive Traits
Heterozygotes are Carriers with a normal phenotype.
Most affected children have normal parents. (Aa x Aa)
Two affected parents will always produce an affected child. (aa x aa)
Two unaffected parents will not produce affected children unless both are Carriers. (AA x AA, AA x Aa)
Affected individuals with homozygous unaffected mates will have unaffected children. (aa x AA)
Close relatives who reproduce are more likely to have affected children.
Both males and females are affected with equal frequency.
Pedigrees show both male and female carriers.

92. Examples of Autosomal Recessive Disorders
Congenital Deafness
Diabetes Mellitus
Sickle Cell anemia
Albinism
Phenylketoneuria (PKU) – Inability to break down the amino acid phenylalanine. Requires elimination of this amino acid from the diet or results in serious mental retardation.
Galactosemia – enlarged liver, kidney failure, brain and eye damage because can’t digest milk sugar
Cystic Fibrosis – affects mucus and sweat glands, thick mucus in lungs and digestive tract that interferes with gas exchange, lethal.
Tay Sachs Disease – Nervous system destruction due to lack of enzyme needed to break down lipids necessary for normal brain function. Early onset and common in Ashkenazi Jews; results in blindness, seizures, paralysis, and early death.

93. Autosomal Dominant Traits
Heterozygotes are affected
Affected children usually have affected parents.
Two affected parents can produce an unaffected child. (Aa x Aa)
Two unaffected parents will not produce affected children. (aa x aa)
Both males and females are affected with equal frequency.
Pedigrees show no Carriers.

94. Examples of Autosomal Dominant Disorders
Dwarfism
Polydactyly and Syndactyly
Hypertension
Hereditary Edema
Chronic Simple Glaucoma – Drainage system for fluid in the eye does not work and pressure builds up, leading to damage of the optic nerve which can result in blindness.
Huntington’s Disease – Nervous system degeneration resulting in certain and early death. Onset in middle age.
Neurofibromatosis – Benign tumors in skin or deeper
Familial Hypercholesterolemia – High blood cholesterol and propensity for heart disease
Progeria – Drastic premature aging, rare, die by age 13. Symptoms include limited growth, alopecia, small face and jaw, wrinkled skin, atherosclerosis, and cardiovascular problems but mental development not affected.

95. Examples of Sex-Linked Recessive Disorders
Red/Green Colorblindness – Difficulty perceiving differences between colors (red or green, blue or yellow).
Hemophilia – Absence of one or more proteins necessary for normal blood clotting.
Deafness
Cataracts – opacity in the lens that can lead to blindness
Night blindness – (Nyctalopia) rods do not work so that can not see in the dark
Glaucoma – pressure in the eye that can lead to optic nerve damage and blindness
Duchenne Muscular Dystrophy – progressive weakness and degeneration of skeletal muscles that control movement due to absence of dystrophin (protein that maintains muscle integrity). Mainly in boys, onset 3-5 yrs, by 12 years can’t walk, and later needs respirator.

96. Sex-Linked Disorder Linked to sex chromosomes
Recessive Disorders – caused by recessive alleles

97. Sex-Linked Recessive Traits
More males than females are affected.
An affected son can have parents who have the normal phenotype. (XAY x XAXa)
For a daughter to have the trait, her father must also have it. Her mother must have it or be a carrier (XaY, XaXa, XAXa)
The trait often skips a generation from the grandfather to the grandson.
If a woman has the trait (XaXa), all of her sons will be affected.
Pedigrees show only female carriers but no male carriers.

98. Genetic Counselor Activity
Imagine that you are a Genetic Counselor assigned to family to discuss with them the possibility of their child inheriting a genetic disorder.
You are given the family history and whether or not the disorder is Autosomal Dominant or Autosomal Recessive.
Draw Punnett Squares to determine odds of children inheriting the disease and answer the questions on the worksheet.

100. Diagram showing a family tree and patterns of inheritance.
What is a Pedigree???
Diagram showing a family tree and patterns of inheritance.