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M2M Unit 2 > Diseases (Mutations, Phenotypes, etc.) > Flashcards

Diseases (Mutations, Phenotypes, etc.) Flashcards

1
Q

Down Syndrome Mutation

A

Trisomy 21. 3-4% unbalanced 21 translocation. 1% mosaic trisomy. Associated with maternal age, Caused by abnormal non-disjunction (chiasmata too close or too far from centromere)

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2
Q

Down Syndrome Phenotype

A

Rate: 1/800 live births
Normal Size, Midface Hypoplasia, Upslanting Palpebral Features, Epicanthal folds, Small Ears, Large Tongue, Low Muscle Tone, Short Fingers, Increased Joint Mobility, Transverse Palmar Crease,

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3
Q

Down Syndrome Complications

A

Cardiac: 50%, atrioventricular canal common
GI: 10-15%, structural abnormalities (dudenal artresia) and feeding problems, GERD, constipation
Ophthalmic: blocked tear ducts, myopia, lazy eye, nystagmus, cataracts

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4
Q

Duchenne Muscular Dystrophy Clinical

A

Progressive Myopathy. Large calves, Gowers maneuver, abnormal gait, high creatine kinase levels (muscular damage)

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5
Q

Duchenne MD Inheritance/Prominence

A

X-linked recessive, 1 in 3,000 males

Onset at 2 years, Wheelchair bound at 13, death at 18

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6
Q

Duchenne MD Mechanism

A

Loss of function: deletion or frame shift mutation in Dystrophin gene (Xp21.2).
High new mutation rate. In-frame deletion or missense mutations lead to milder Becker’s MD

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7
Q

Duchenne MD Testing

A

Genetic Sequencing: can determine deletion and frame shift mutation.

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8
Q

Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) Clinical

A

Temporary neuropathy following pressure to nerves. Typically full recovery. Onset 20s-30s

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9
Q

HNPP: Inheritance/Prominence

A

Autosomal Dominant

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10
Q

HNPP Mechanism

A

Loss of function, Deletion of PMP22 gene (17p11.2) (glycoprotein in nerves).

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11
Q

HNPP Testing

A

Deletion: FISH, Microarray

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12
Q

Osteoenesis Imperfecta Type 1 Clinical

A

Brittle bones, increased fractures, blue sclerae, normal stature, adult progressive hearing loss

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13
Q

Osteogenesis Imperfecta 1 Inheritance/Prominence

A

Autsomal Dominant

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14
Q

Osteogenesis Imperfecta 1 Mechanism

A

Loss of function nonsense frame mutation in COL1A1 gene (early termination). Unstable mRNA that gets degraded, loss of collagen 1, decreases collagen strength

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15
Q

Osteogenesis Imperfecta 1 Testing

A

DNA sequencing for mutation in gene

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16
Q

Charcot-Marie-Tooth Type 1A Clinical

A

Demyelinating motor and sensory neuropathy, lower extremity weakness, muscle atrophy, and sensory loss.

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17
Q

CMT 1A Inheritance/Prominence

A

Autosomal Dominant

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18
Q

CMT 1A Mechanism

A

Gain of function duplication of PMP22 gene (17p11.2)

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19
Q

CMT 1A Testing

A

Duplication tested by FISH, Microarray, DNA sequencing

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20
Q

Osteogenesis Imperfecta II-IV Clinical

A

Brittle bones, increased fractures, blue sclerae

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21
Q

Ost Imperfecta II-IV Inheritance

A

Autosomal Dominant

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22
Q

Ost Imperfecta II-IV Mechanism

A

Novel Property Mutation: Collagen 1A2 has different folding due to mutation. Still forms trimers with Collagen 1.

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23
Q

Ost Imperfecta II-IV Testing

A

DNA sequencing?

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24
Q

Huntington Disease Clinical

A

Progressive neurodegeneration as adult, corea, death within 15 years of onset

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25
Q

Huntington Disease Inheritance

A

Autosomal Dominant, 1/10,000: presence with # of repeats
Genetic Anticipation: # of repeats likely to increase in subsequent generations 2’ to slippage. Maternal expansions more likely.

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26
Q

Huntington Disease Mechanism

A

Increase in # of CAG (glutamate) repeats in Huntington gene (4p16.3).
Ranges: 39 full penetrance; >60 juvenile onset

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27
Q

Huntington Disease Testing

A

Trinucleotide Repeat: Fish? DNA Sequencing gives specific number

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28
Q

Myotonic Dystrophy Clinical

A

Droopy eyes, intellectual difficulty, hypotonia

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29
Q

Myotonia Dystrophy Inheritance

A

Autosomal Dominant

30
Q

Myotonia Dystrophy Mechanism

A

Increase of CTG repeats within 3’ UTR of DMPK gene

31
Q

Myotonia Dystrophy Testing

A

Trinucleotide repeats: DNA sequencing

32
Q

Phenylketouria Clinical

A

Early onset epilepsy, hyperactivity, intellectual delay

33
Q

PKU Inheritance

A

Autosomal Recessive, High allelic heterogeneity w/ 400 mutant alleles

34
Q

PKU Mechanism

A

Loss of function: Defect in phenylalanine hydroxylase enzyme which converts phenylalanine to tyrosine most common. Also possible to have BH4 deficiency (cofactor also used in dopamine and seratonin synthesis)

35
Q

PKU Testing / Screening

A

Newborn screening post partum when mother’s enzymes gone, can change diet to prevent effects
Mass Spectrometry: fast detection of amount of enzyme in blood.
Guthrie test: too much PA let bacteria grow

36
Q

PKU Treatment

A

Low phenylalanine diet. Maintained during pregnancy to prevent complications
BH3 replacement PO

37
Q

Alpha 1 Trypsin Deficiency Clinical

A

Adult onset, increased risk of emphysema and liver cirrhosis/cancer

38
Q

ATD Inheritance

A

Autosomal Recessive. 1/2500. 1/25 carriers.

39
Q

ATD Mechanism

A

Loss of SERPINA1 protein is inhibitor of elastase. Elastase released in lungs by neutrophils, if not degraded it destroys lung elastin. Process accelerated by smoking b/c more neutrophils recruited to lungs.

40
Q

ATD Allelic Heterogeneity

A 
M allele normal, most common
Z allele (Glu342Lys) misfolded protein that accumulates in ER of liver cells. 
S allele (Glu264Val) unstable, less effective protein
Z/S intermediate between Z/Z and S/S
41
Q

ATD Testing

A

Sequencing for point mutations, FISH probes for each allele, Enzyme function tests

42
Q

ATD Treatment

A

Enzyme infusion and aerosol treatment

43
Q

Tay-Sachs Disease Clinical

A

Progressive CNS neurodegeneration, onset 3-6 months. Muscle weakness, decreased attentiveness, startling at sound. Then seizures, vision/hearing loss, reduced mental function, paralysis. “Cherry red spot in eye”. Death at 3-4 years

44
Q

Tay-Sachs Inheritance

A

Autsomal Recessive. 1/360,000 general; 1/3,600 Aschkenazi Jewish

45
Q

T-S Mechanism

A

LSD, defect in HexA subunit of GM2 degrading complex. GM2 cannot be degraded, aggregates in lysosomes of CNS neurons.
Allelic heterogeneity: 4 bp insertion frame shift mutation most common

46
Q

T-S Screening/Testing

A

Screen potential carriers for enzyme function, test for 3 main mutant alleles in parents and child

47
Q

Sandhoff Disease

A

Similar to T-S but mutation in HexB subunit

48
Q

AB-Variant of T-S

A

Severe form of T-S where HexA and HexB are fine but mutation in GM2AP prevent normal funciton.

49
Q

Cystic Fibrosis Clinical

A

Salty skin, poor growth and weight gain, mucus accumulation, chest infections, coughing and SOB

50
Q

Cystic Fibrosis Inheritance

A

Autosomal Recessive

51
Q

Cystic Fibrosis Mechanism

A

Loss of function mutation of CFTR gene

52
Q

Achondroplasia Clinical

A

Short Stature, Rhizomelic limb shortening, large head, megalencephaly, trident hand, spinal cord compression 2’ to small foramina. Brain stem compression = 3-7% early death

53
Q

Achondroplasia Inheritance

A

Autosomal Dominant. 1/40,000. Homozygous is lethal!

54
Q

Achondroplaisa Mechanism

A

Gain of function mutation Gly380Arg in FGFR3 gene. Tyrosine kinase constitutively on, inhibits bone growth. Mutations in father’s germline.

55
Q

Neurofibromatosis Clinical

A

Cafe au lait spots, axillary and inguinal freckling, multiple neurofibromas, Lish nodules on eyes. 100% penetrant.

56
Q

Neurofibromatosis Inheritance

A

Autosomal Dominant

57
Q

Neurofibromatosis Mechanism

A

Mutation of NF1 gene on chromosome 17

58
Q

Marfan Syndrome Clinical

A

Connective tissue disorder with ocular, skeletal, and cardiac manifestation. Tall and skinny. Hypermobile joint, pectus excatum. Risk of Aortic Aneurysm

59
Q

Marfan Syndrome Inheritance

A

Autosomal Dominant 1/5,000

60
Q

Marfan Syndrome Mechanism

A

Mutation in FBN1 gene (fibrillin)

61
Q

Familial Hypercholesteremia

A

High cholesterol levels from mutations in LDL receptor so it can’t clear LDL from bloodstream

62
Q

Fragile X Clinical

A

Childhood onset mental deficiency, dysmorphic facies, enlarged testicles, speech delay, autism-like, large ears and prominent jaws

63
Q

Fragile X Inheritance

A

X-linked dominant

64
Q

Fragile X Mechanism

A

Trinucleotide expansion in 5’ UTR of fragile X region leading to hypermethylation. Haplotype effect.
Ranges: Grey zone 6-45; Premutation 59-200; penetrance 200+
Maternal genetic anticipation.

65
Q

Fragile X Premutations

A

FTAXS (59-200 repeats): adult onset tremor, ataxia, Parkinsonian features, memory loss. Women also premature ovarian failure.
From increased RNA production, sites not hypermethylated yet

66
Q

Hemophilia A Clinical

A

Reduced clotting

67
Q

Hemophilia A Inheritance

A

X-linked Recessive

68
Q

Hemophilia A Mechanism and Treatment

A

Factor VIII deficiency, fixed with Factor VIII supplementation

69
Q

Turner Syndrome Clinical

A

Gonadal Dysgenesis, short stature, heart defects, fused kidneys, webbed neck, brown nevi, wide nipple placement, infertility, social difficulties, difficulty with math

70
Q

Turner Syndrome Inheritance and Mechanism

A

45 X0; 1/2,000-5,000 live births; Meiotic non-disjunction

71
Q

Klinefelter Syndrome Clinical

A

Gonadal dysgenesis/hypogonadism, infertility, tall stature, gynecomastia, likely sterile, language trouble

72
Q

Klinefelter Inheritance and Mechanism

A

47, XXY; Meiotic Nondisjuction

M2M Unit 2 (1 decks)

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