Mendelian Inheritance

Question 1

Genes do not exist in isolation

Answer 1

They interact with each other and the environment

Question 2

Genetic mechanisms of disease

Answer 2

Loss of function: DMD and dystrophin
Gain of function: Oncogenes (cancer)
Protein alteration: Sickle Cell

Question 3

Pedigree Nomenclature

Answer 3

Squares = Male
Circles = Female
Double bond = Consanguineous mating (cousins)
Dark shade = affected
Light shade = are affected but do not express it

Men are always listed first.

Question 4

Autosomal Dominant

Answer 4

1. Affected offspring have one affected parent
2. Trait is expected in every generation
3. Trait inherited at roughly 50%

Question 5

Autosomal Recessive

Answer 5

1. Most affected individuals have normal parents (carriers)
2. On average 1:4 affected
3. Can skip generations
4. More common among consanguinity
5. Sickle cell anemia

Question 6

X-linked Recessive

Answer 6

1. When males have it, termed hemizygous
2. Females can be homo or heterozygous
3. DMD, Duchenne Muscular Dystrophy
4. Unaffected males do not transmit trait
5. All daughters of affected males are carriers

Question 7

X-linked Dominant

Answer 7

1. VERY RARE
2. No carriers
3. Rickets, abnormal Vitamin D metabolism
4. Affected females transmit to 50% of offspring
5. Affected males transmit only to females, 100%

Question 8

Penetrance

Answer 8

1. Have the genotype but don’t show the phenotype
2. Frequency that gene shows itself is penetrance
3. Lightly shaded boxes indicate people who do not express phenotype of disorder

Question 9

Variable Expressivity

Answer 9

1. Range of phenotypes associated with a specific genotype
2. Shows variable expressivity
3. Cafe-au-lait spots