Exam 1 (2/6)

Question 1

Mendelian phenotype

Answer 1

Controlled by one gene (monogenic)

Question 2

Mendelian disease

Answer 2

Caused by mutation of a single gene / locus; mutated gene is (mostly) necessary and sufficient for disease onset

Question 3

Classifications of peripheral neuropathies

Answer 3

1. Acquired neuropathies
2. Neuropathies associated with other disorders
3. Inherited neuropathies

Question 4

Charcot-Marie-Tooth (CMT) disease

Answer 4

Hereditary disorder giving rise to distal limb
weakness, maximal in the lower
extremities

Question 5

Locus heterogeneity

Answer 5

A single disorder, trait, or pattern of traits caused by mutations in genes at different chromosomal loci

Question 6

Allelic heterogeneity

Answer 6

A single disorder, trait, or pattern of traits caused by different mutations within a gene

Question 7

Clinical heterogeneity

Answer 7

The production of clinically different phenotypes, even among patients with the same mutation

Question 8

CMT1

Answer 8

Primary demyelination; defect in myelinating Schwann cell

Question 9

CMT2

Answer 9

Primary axon loss; no demyelination; defect in axon

Question 10

Male pedigree symbol

Answer 10

Square

Question 11

Female pedigree symbol

Answer 11

Circle

Question 12

Sex removed or unknown pedigree symbol

Answer 12

Diamond

Question 13

Unaffected pedigree symbol

Answer 13

Unshaded

Question 14

Affected pedigree symbol

Answer 14

Shaded

Question 15

Carrier pedigree symbol

Answer 15

Shaded circle in center

Question 16

Five major mendelian inheritance patterns

Answer 16

1. Autosomal dominant
2. Autosomal recessive
3. X-linked dominant
4. X-linked recessive
5. Y-linked

Question 17

Autosomal dominant

Answer 17

One mutant copy necessary and sufficient for disease; affected individual has one
affected parent; 50% chance of transmission to next generation

Question 18

Autosomal recessive

Answer 18

Two mutant copies necessary and
sufficient for disease; affected individuals born to unaffected parents (carriers); siblings of affected individuals have a 25% chance of being affected

Question 19

X-linked dominant

Answer 19

One mutant X is N/S; more females than males affected but females have milder phenotype; child of affected female has 50% chance of being affected regardless of sex; all daughters of affected males will be affected; all sons of affected males will be unaffected

Question 20

X-linked recessive

Answer 20

One mutant X is N/S in the absence of an unmutated WT X; mainly affects males (hemizygous); affected males born to unaffected parents; females affected if father affected/mother carrier or WT X is inactivated; no male-to-male transmission

Question 21

Y-linked

Answer 21

Affects only males; affected males always have an affected father and affected offspring

Question 22

Explanations for simplex pedigree (only one affected individual)

Answer 22

1. AR or XLR
2. De novo AD mutation
3. AD with low penetrance
4. Phenocopy (nongenetic)

Question 23

Incomplete penetrance

Answer 23

A subset of individuals with the mutation(s) (required genotype) do not develop the disease

Question 24

Age of onset

Answer 24

Some phenotypes present at different life stages and the age of onset can vary (e.g., adult onset neurodegenerative disease)