Genetics

Question 1

Codominance

Answer 1

both alleles contribute to the phenotype

Question 2

Variable Expressivity

Answer 2

Phenotype varies among individuals with the same phenotype

Question 3

Incomplete Penetrance

Answer 3

Not all individuals with a specific genotype show the phenotype

Question 4

Pleiotropy

Answer 4

One gene contributes to multiple phenotype effects

Question 5

Anticipation

Answer 5

Increased severity or early onset of disease in succeeding generations

Question 6

Dominant Negative Mutation

Answer 6

Heterozygote produces a nonfunctional altered protein that prevents the normal one form functioning

Question 7

Linkage Disequilibrium

Answer 7

Tendency of alleles at linked loci to occur together more or less often than expected by chance

Question 8

Locus Heterogeneity

Answer 8

Mutations at different loci produce the same/similar phenotype

Question 9

Allelic Heterogeneity

Answer 9

Different mutations in the same locus produce the same phenotype

Question 10

Heteroplasmy

Answer 10

presence of both normal and mutated mitochondrial DNA

Question 11

Heterozygous Uniparental Disomy

Answer 11

Occurs with meiosis I error

Question 12

Homozygous Uniparental Disomy

Answer 12

Occurs with meiosis II error

Question 13

Prader-Willi Syndrome

Answer 13

Silent maternal gene, deleted/mutated paternal

25% are maternal uniparental disomy

Question 14

Angelman syndrome

Answer 14

Silent paternal gene, deleted/mutated maternal gene

only 5% are paternal uniparental disomy

Question 15

Autosomal Dominant Polycystic Kidney Disease

Answer 15

85% are PKD1 mutation (chr 16) remainder are PKD2 (chr 4)

Bilateral enlarged kidneys, cysts

Question 16

Familial Adenomatous Polyposis

Answer 16

chromosome 5q (APC) mutation
Colon covered in polyps, resect or develop cancer

Question 17

Familial Hypercholesterolemia

Answer 17

Defective or absent LDL Receptor

Question 18

Hereditary Hemorrhagic Telangectasia

Answer 18

Branching skin lesions, recurrent epistaxis, skin discoloration, GI bleeding, hematuria

Question 19

Hereditary Spherocytosis

Answer 19

spectrin or ankryn defects cause hemolytic anemia

Question 20

Huntington Disease

Answer 20

CAG trinucleotide repeat on chromosome 4

Exhibits anticipation

Question 21

Li-Fraumeni Syndrome

Answer 21

TP53 abnormality, many cancers at early age

Question 22

Marfan Syndrome

Answer 22

FBN1 mutation on chromosome 15 (fibrin)

Sympt: tall, long extremities, pectus excavatum, medial necrosis of aorta, floppy mitral valve

Question 23

Multiple endocrine neoplasias

Answer 23

Familial tumors of endocrine glands

Question 24

Neurofibromatosis type I

Answer 24

Café au lait spots, cutaneous neurofibromas, optic gliomas, pheochromocytomas, Lisch nodules
AD, 100% penetrant with variable expression
Mutation in NF1 gene on chr 17

Question 25

Neurofibromatosis type II

Answer 25

bilateral acoustic schwannomas, juvenile cataracts, meningiomas
Mutation in NF2 on chromosome 22

Question 26

Tuberous Sclerosis

Answer 26

numerous benign hamartomas

Incomplete penetrance, variable expression

Question 27

von Hippel Lindau

Answer 27

Numerous tumors, associated with VHL deletion on chromosome 3

Question 28

Cystic Fibrosis

Answer 28

Most common caucasian genetic disease, CFTR defect on chromosome 7.
Most common mutation is folding problem that traps in RER, less chloride out keeps water in and draws sodium in. Thick secretions.
High chloride in sweat.

Question 29

Duchenne MD

Answer 29

Frameshift truncating dystrophin protein, longest protein in human body on X chromosome.
Onset before 5 years, Gower maneuver, pseudohypertrophy of calf

Question 30

Dystrophin

Answer 30

Connects cytoskeleton to alpha and beta dystroglycan transmembrane proteins which connect to the ECM

Question 31

Becker MD

Answer 31

Non-frameshift, insertions into dystrophin so it is partially functional

Question 32

Myotonic Dystrophy Type I

Answer 32

AD, CTG trinucleotide repeat expansion of DMPK gene

Symptoms: My Tonia, My Testicles (atrophy), My Toupee (Frontal balding), My Ticker (Arrhythmia)

Question 33

Fragile X

Answer 33

CGG trinucleotide repeat of FMR1 gene

Symptoms: enlarged testicles, large jaw, large ears, autism, mitral prolapse

Question 34

Trinucleotide Repeat Diseases

Answer 34

Fragile X Syndrome, X, FMR1, CGG
Friedreich Ataxia, GAA
Huntington Chr 4, Huntington, CAG
Myotonic Dystrophy, DMPK, CTG

Try Hunting for My Fried Eggs
X-Girlfriend’s First Aid Helped Ace My Test

Question 35

Down Syndrome

Answer 35

Trisomy 21, 1:700

Symptoms: retardation, flat facies, single palmar crease, early onset Alzheimer’s, high risk of AML/ALL, etc.

Associated w/ maternal nondisjunction in 95% of cases, 4% Robertsonian translocation, 1% mosaicism

1st Trimester: serum PAPP-A is low, free beta-HCG is high
2nd Trimester: low alpha-fetoprotein, high beta-HCG, low estriol, high inhibin A

Question 36

Edwards Syndrome

Answer 36

Trisomy 18; 1:8000

Symptoms: retardation, rocker-bottom feet, micrognathia, low set ears, clenched hands

First trimester: low PAPP-A & beta-HCG
Second Trimester: low alpha fetoprotein, beta-HCG, estriol, inhibin A

Question 37

Patau Syndrome

Answer 37

Trisomy 13; 1:15000

Symptoms: retardation, rocker-bottom feet, microphthalmia, microcephaly, cleft lip/palate, holoprosencephaly, polydactyly

First Trimester: low beta-HCG, PAPP-A and increased nuchal translucency

Question 38

Cri-du-chat Syndrome

Answer 38

microdeletion of short arm of chromosome 5

Symptoms: microcephaly, retardation, high pitched crying, epicanthal folds

Question 39

Williams Syndrome

Answer 39

Microdeletion of long arm of chromosome 7 (elastin)

Symptoms: “elfin” facies, retardation, hypercalcemia, extreme friendliness

Question 40

22q11 Deletion Syndromes

Answer 40

Adherent development of 3 and 4 branchial pouches
Symptoms are CATCH-22

Cleft palate
Abnormal facies
Thymic aplasia (t cell deficient) 
Cardiac defects
Hypocalcemia

Question 41

Two 22q11 deletion syndromes

Answer 41

DiGeorge Syndrome (thymus, thyroid, and cardiac defects)
Velocardiofacial syndrome (palate, facial, and cardiac defects)