genetics

Question 1

variable expressivity

Answer 1

phenotype varies among affected individuals (example- NF1)

Question 2

incomplete penetrance

Answer 2

not all patients with genotype will express mutant phenotype

Question 3

pleiotropy

Answer 3

one gene has effects on multiple organ systems

Question 4

locus heterogenicity

Answer 4

mutations at different loci produce the same phenotype, example- marfan syndrome, MEN2B and homocystinuria all have marfanoid habitus

Question 5

heteroplasmy

Answer 5

presence of normal and mutated tDNA, resulting in variable mitochondrial disease inheritance

Question 6

hardy-weinberg equations (2)

Answer 6

p^2 + 2pq + q^2 = 1

p + q = 1

Question 7

imprinting

Answer 7

at some loci, only 1 allele is active and the other is inactivated by methylation = imprinting

Question 8

prader-willi syndrome

Answer 8

paternal allele on 15q11-13 not expressed

Question 9

angelman syndrome

Answer 9

maternal allele on 15q11-13 not expressed

Question 10

typical of AD inheritance

Answer 10

every generation
males = females
structural genes
presents in adulthood

Question 11

typical of AR inheritance

Answer 11

skips generations
males=females
enzymes 
present in childhood, more severe
increased with consanguinity

Question 12

x-linked recessive

Answer 12

present in males of carrier mothers

females carriers

Question 13

x-linked dominant disorders (4)

Answer 13

hypophosphatemic rickets, fragile-X, rett syndrome, charcot-marie-tooth

Question 14

mitochondrial disease

Answer 14

transmitted to all offspring of affected mother

Question 15

buzzword for mitochondrial disease

Answer 15

ragged red fibers

Question 16

tuberous sclerosis (5 findings)

Answer 16

ash leaf spots
angiomyolipoma of kidney
mental retardation
seziures 
cardiac rhabdomyomas

Question 17

cystic fibrosis defect, inheritance

Answer 17

CTFR gene on chromosome 7

AR

Question 18

normal activity of CTFR

Answer 18

secretes Cl in lungs/Gi

reabsorbs Cl from sweat

Question 19

most common CTFR mutation

Answer 19

delta F508= protein misfolding that leads to destruction of Cl channel before it reaches cell surface

Question 20

N-acetylcysteine MOA

Answer 20

loosens mucus by cleaving disulfide bonds

Question 21

fragile X cause, inheritance

Answer 21

defect of methylation and expression of FMR1 gene, X-linked dominant

Question 22

physical features of fragile X (4)

Answer 22

long face/large jaw
large testes
autism
mitral valve prolapse

Question 23

Huntington disease (repeat, location)

Answer 23

CAG on chromosome 4

Question 24

fragile X

Answer 24

CGG on X chromosome

Question 25

friedreich’s ataxia

Answer 25

GAA on chromosome 9

Question 26

myotonic dystrophy

Answer 26

CTG

Question 27

mneumonic for trinucleotide repeats

Answer 27

X-girlfriend’s First Aid Helped Ace My Test

Question 28

most common heart defect in T21

Answer 28

ostium primum type ASD

Question 29

classic heart defect in T21

Answer 29

AV canal due to endocardial cushion defects

Question 30

quad screen in T21

Answer 30

decreased AFP, estriol

increased bHCG, inhibit A

Question 31

edward syndrome

Answer 31

trisomy 18

Question 32

characteristic feature of T18

Answer 32

clenched fists with overlapping digits

Question 33

patau syndrome

Answer 33

trisomy 13

Question 34

characteristic features of T13 (2)

Answer 34

holoprosencephaly, cleft lip/palate

Question 35

cri-du-chat cause

Answer 35

micro deletion of 5p

Question 36

cri-du-chat symptoms

Answer 36

high pitched cry (due to del of genes involved in development of larynx)

Question 37

williams syndrome cause

Answer 37

microdeletion 7q

Question 38

williams syndrome symptoms (3)

Answer 38

elfin facies, extreme friendliness with strangers, hypercalcemia (high sensitivity to it D)