Pedigree and Inherited Disease Examples

Question 1

How to recognize Autosomal Dominant Inheritance (3 things are listed)

Answer 1

• Appears in every generation (except for new mutations) - vertical pedigree
• Affected people have at least one affected parent
• Males and females equally affected, equal transmission to both sons and daughters

Question 2

How to recognize Autosomal Recessive Inheritance (3 things listed)

Answer 2

• Does not appear in every generation (horizontal pedigree)
• Males and females equally affected, equal transmission to both sons and daughters
• More likely to show an example of consanguineous marriage

Question 3

5 examples of Autosomal Recessive Disorders + their mutations
(only listed some common ones listed on department ppts)

Answer 3

1. Phenylketonuria (PAH: phenylalanine hydroxylase)
2. Albinism (tyrosinase)
3. Cystic Fibrosis (CFTR)
4. Sickle Cell Anemia (beta globin)
5. Thalasemia (beta globin)

Note these are usually severe defects of enzymes, and heterozygous carriers often have some evolutionary advantage

Question 4

5 common examples of Autosomal Dominant Disorders + their mutations

Answer 4

1. Osteogenesis imperfecta (collagen)
2. Achondroplasia (FGFR3)
3. Huntington Chorea (Huntingtin)
4. Marfan syndrome (fibrillin)
5. Familial Hypercholesterolemia (LDLR)

Note these are usually less severe or have later-onset health effects than AR diseases

Question 5

How to identify X-linked Dominant Inheritance (3 things)

Answer 5

• Affected men can never transmit an affected X to their son, but always to daughter
• Affected mothers can transmit affected X to sons and daughters
• Usually appears in every generation

Question 6

How to identify X-linked recessive inheritance (4 things)

Answer 6

• Skips generations (horizontal pedigree)
• Almost always appears in male (needs affected male survivor + carrier mother to be in female)
• Affected males cannot give affected X to sons, but affected males always produce carrier daughters
• If there is an affected female, all her sons are affected and her daughters are carriers

Question 7

3 examples of X-linked Dominant Inheritance + their mutations

Answer 7

1. Amelogenesis imperfecta (amelogenin)
2. Hypophosphatemia (PHEX: phosphate regulating endopeptidase)
3. Fragile X syndrome (FMR1)

Question 8

3 examples of X-linked Recessive Inheritance + their mutations

Answer 8

1. Duchenne and Becker Muscular Dystrophy (dystrophin)
2. Red-Green Color Blindness (actually multiple forms, dont need to know mutation)
3. Hemophilia A, B (coagulation factors VIII or IX… note that hemophilia C is autosomal recessive)

Question 9

How to identify Y-linked inheritance

Answer 9

• Only males are affected, see male-to-male transmission

- Appears in every generation (vertical pedigree)

Question 10

An example of Y-linked inherited disorder

Answer 10

Azoospermia: not normally able to be transmitted, but theoretically could be through in vitro fertilization with intracytoplasmic sperm injection

Other than that, not really any known

Question 11

How to identify mitochondrial inheritance?

Answer 11

• Maternal inheritance, all children of affected mother have the disease
• Affected fathers never transmit to children

Question 12

An example of mitochondrial inheritance

Answer 12

Leber’s optic atrophy (LHON gene, Lebers hereditary optic neuropathy. plus other various mtDNA mutations.)

MTC mutations tend to impact areas that need a lot of ATP, like the nervous system