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FIRST AID > Biochem: genetics > Flashcards

Biochem: genetics Flashcards

1
Q

What is codominance?

A

both alleles contribute to the phenotype of the heterozygote

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2
Q

What is variable expressivity?

A

phenotype varies among individuals with same genotype

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3
Q

What is incomplete penetrance?

A

not all individuals with a mutant genotype show the mutant phenotype

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4
Q

What is pleiotropy?

A

one gene contributes to multiple phenotypic effects

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5
Q

What is imprinting?

A

differences in gene expression depend on whether the mutation is of maternal or paternal origin

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6
Q

What is anticipation?

A

increased severity or earlier onset of disease in succeeding generations

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7
Q

What is loss of heterozygosity?

A

if a patient inherits or develops a mutation in a tumor suppressor gene, the complementary allele must be deleted/mutated before cancer develops (not true of oncogenes)

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8
Q

What is a dominant negative mutation?

A

exerts a dominant effect

a heterozygote produces a nonfunctional altered protein that also prevents the normal gene product from functioning

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9
Q

What is linkage disequilibrium?

A

tendency for certain alleles at 2 loci to occur together more often than expected by change
measured in a population, not in a family, often varies in different populations

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10
Q

What is mosaicism?

A

Occurs when cells in the body differ in genetic makeup due to postfertilization loss or change of genetic information during mitosis (can be germline-produce disease that is not carried by parent’s cells)

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11
Q

What is locus heterogeneity?

A

mutations at different loci can produce the same phenotype

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12
Q

What is heteroplasmy?

A

the present of both normal and mutated mtDNA, results in variable expression in mitochondrial inherited disease

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13
Q

What is uniparental disomy?

A

offspring receives 2 copies of a chromosome from 1 parent and no copies from the other parent
heterodisomy (heterozygous) indicates a meisosi I error
isodisomy (homozygous) indicates a meiosis II error or postzygotic chromosomal duplication of one of a pair of chromosomes and loss of the other of the originial pair

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14
Q

Which allele is not expressed in Prader Willi? Sx?

A

paternal not expressed (and maternal gene is inactivated)

MR, hyperphagia, obesity, hypogonadism, hypotonia

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15
Q

Which allele is not expressed in Angelmans? Sx?

A

maternal allele is not expressed (and paternal gene is inactivated)
MR, seizures, ataxia, inappropriate laughter

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16
Q

What is the most common inheritance of enzyme deficiency diseases?

A

AR

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17
Q

What is hypophosphatemic rickets?

A

X linked dominant disorder resulting in increased phosphate wasting at proximal tubule, results in rickets-like presentation

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18
Q

What are key features of mitochondrial myopathies?

A

usually present with myopathy and CNS disease

muscle biopsy often shows “ragged red fibers”

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19
Q

Cause, sx and inheritance of achondroplasia?

A

defect in FGF3-R, dwarfism, short limbs, large head, normal trank size
advanced paternal age assoc
AD

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20
Q

Caus, sx and inheritand of ADPKD?

A

bitlateral massive enlargement of kidneys due to multiple large cysts, flank pain, hematuria, hypertension, progressive renal failure
PKD1 gene mutation, chromosome 16
assoc w/polycystic liver disease, berry aneurysms, MVP
AD

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21
Q

Cause, sx and inheritance of FAP?

A

AD
colon cvered in polyps that progress to colon cancer unless colon resected
APC on chromosome 5 mutated

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22
Q

Cause, sx and inheritance of Gardner’s syndrome?

A

AD

tumors in colon and other soft tissues

23
Q

Cause, sx and inheritance of familial hypercholesterolemia (hyperlipidemia IIA)?

A

elevated LDL due to defective or absent LDL-R, severe atherosclerotic disease early in life, tendon xanthomas, MI before age 20
AD

24
Q

Cause, sx and inheritance of Osler-Weber-Rendu Syndrome?

A

aka hereditary hemorrhagic telangiectasia
AD
inherited disorder of BVs
telangiectasia, recurrent epistaxis, skin discolorations, AVMs, chronic GI bleeding

25
Q

Cause, sx and inheritance of hereditary spherocytosis?

A

spheroid erythrocytes due to spectrin or ankyrin defect, hemolytic anemia, increased MCHC, increased viscosity, hemolytic anemia, jaundice
splenectomy is curative

26
Q

Cause, sx and inheritance of Huntington’s disease?

A

AD
CAG repeat chromosome 4
decreased GABA and ACh in brain
cognitive decline, caudate atrophy, chroea

27
Q

Cause, sx and inheritance of marfans?

A

AD
fibrillin 1 gene mutation
AAA, floppy mitral valve, subluxation of lenses

28
Q

Cause, sx and inheritance of multiple endocrine neoplasias?

A

AD
familiar tumors of endocrine glands
2A and 2B assoc w/ret gene mutations

29
Q

Cause, sx and inheritance of NF-1?

A

AD
chromosome 17 has mutation
cafe au lai spots, neural tumors, lisch nodules, scoliosis/kyphosis, optic pathway gliomas

30
Q

Cause sx and inheritance of NF-2?

A

AD
NF2 gene on chromosome 22 mutated
bilateral acoustic schwannomas, juvenile cataracts, balance issues

31
Q

Cause, sx and inheritance of Tuberus sclerosis?

A 
AD w/incomplete penetrance/variable presentation
facial lesions (adenoma sebaceum), hypopigmented ashleaf spots, cortical and retinal hamartomas, seizures, MR, renal cysts, renal angiomyolipomas cardiac rhabdomyomas, increased incidence of astrocytomas
32
Q

Cause, sx and inheritance of von Hippel Lindau?

A

AD
deletion of VHL gene on chromosome 3 (leads to constitutive expression of HIF and activation of angiogenic growth factors)
hemangioblastomas of retina/cerebellum/medulla, multiple bilateral renal cell carcinomas and other tumors

33
Q

List the key autosomal recessive disease to know (10)

A

albiniskm, ARPKD, CF, glycogen storage diseases, hemochromatosis, mucopolysaccharidoses, PKU, sickle cell, sphingolipidoses, thalassemias

34
Q

What is the most common mutation seen in CF? What happens to the protein?

A

deletion of Phe 508 of CFTR gene on chromosome 7

causes abnormal folding and usually degradation of channel before reaching cell surface

35
Q

Why can CF cause infertility in men?

A

bilateral absence of vas deferens

36
Q

What are the most important X linked recessive disorders to know? (10)

A 
Bruton's agammaglobulinemia
Wiskott-Aldrich s/o
Fabry's disease
G6PD def
Ocular albinism
Lesch Nyhan
Duchenne's and Beckers Muscular dystrophy
Hunter s/o
Hemophilia A&B
OTC deficiency
37
Q

How are muscular dystrophies diagnosed?

A

increased CPK and muscle biopsy

38
Q

What gene is deleted/mutated in muscular dystrophies?

A

dystrophin

39
Q

What causes Fragile X s/o? Sx?

A

Xlinked
methylation/expression FMR1 gene affected due to CGG repeat
2 mcc of MR
marcroorchidism, long face w/a large jaw, large everted ears, autism or ADHD, MVP
short, joint laxity, scoliosis, pes cavus, dbl jointed thumbs, single palmar crease

40
Q

What are the trinucleotide repeat diseases and their trinucleotides?

A 
Fragile X=CGG
Friedrich ataxia=GAA
Huntingons=CAG
Myotonic dystrophy=CTG
** these often show anticipation
41
Q

What causes Cri-du-chat s/o?

A

microdeletion of short arm of chromosome 5

42
Q

Sx of cri-du-chat?

A

microcephaly, MR, high pitched crying/mewing, epicanthal folds, cardiac abnormalities (VSD)

43
Q

What causes Williams s/o?

A

microdeletion of long arm of chromosome 7

44
Q

sx of williams s/o?

A

elfin facies, intellectual disability, hypercalcemia (increased Vit D sensitivity), well developed verbal skills, extreme friendliness with strangers, CV problems

45
Q

What can 22q11 deletion syndromes cause?

A

CATCH-22
cleft palte, abnormal facies, thymic aplasia, carrdiac defects (tetralogy), hypocalemia 2ary to parathyroid aplasia
DiGeorge s/o
velocardiofacial s/o

46
Q

What is a robertsonian translocation?

A

nonreciprocal chromosomal translocation that commonly involves chromosome pairs 13,14,15,21,22
common
occurs when long arms of 2 acrocentric chromosomes fuse at the centromere and the short arms are lost
unbalanced translocations can result in miscarriage, stillbirth and chromosomal imbalance (down’s, patau’s)

47
Q

What are sx of trisomy 21?

A

MR (mcc)
flat facies, prominent epicanthal folds, simian crease, gap bwn 1st 2 toes, duodenal atresia, congenital heart disease (mc ASD), increased risk of ALL, alzheimers disease

48
Q

What causes trisomy 21?

A 
meiodtic nondisjunction (95%)-assoc w/adv mat age
robertsonian translocation (4%)
down mosaicism (1%)
49
Q

What as sx of trisomy 18 (edwards syndrome)?

A

severe MR, rocker bottom feet, micrognathia, low set ears, clenched hands, prominent occiput, congenital heart disease
death within a year usually

50
Q

What are sx of trisomy 13 (patau’s syndrome)?

A

severe MR, rocker bottom feet, microphthalmia, microcephaly, clef lip/palate, holoprosencephaly, polydactyly, congenital heart disease
death within first year
(may be due to defective sonic hegehog gene)

51
Q

What is seen on pregnancy quad screen w/trisomy 21?

A

decreased AFP, increased B hCG, decreased estriol, increased inhibin A

52
Q

What may be seen on US during first trimester in tri 21 or with triosmy 13?

A

increased nuchal translucency

53
Q

What is seen on preg quad screen w/trisomy 18?

A

decreased AFP, decreased B hCG, decresaed estriol, normal inhibin A

54
Q

What is seen on rpeg quad screen for trisomy 13?

A

decrased free B hCG, decreased PAPP-A

FIRST AID (8 decks)

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