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Medical Genetics Flashcards

1
Q

Carbamoyl phosphate synthetase deficiency

A

Urea cycle disorder that results in the accumulation of N-acetyl glutamic acid due to CP synthetase deficiency

Lethargy, coma

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2
Q

Ornithine transcarbamoylase deficiency

A

Urea cycle disorder that results in the accumulation of carbamoyl phosphate

Most common urea cycle defect (X linked)

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3
Q

Argininosuccinate synthetase deficiency

A

Urea cycle disorder that has an accumulation of citrulline

Lethargy, coma

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4
Q

Arginosuccinase deficiency

A

Urea cycle disorder characterized by a buildup of argininosuccinate due do deficiency of enzyme

Lethargy, coma

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5
Q

Cystinuria

A

Defect in Cystine transporter in the kidneys

Cystine is a dimer of cysteine, precipitates out of soln in high conc, leading to repeated kidney stones

Drink lots of H2O and take drugs to incr pH in urine to make cystine more soluble

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6
Q

Wilson Disease

A

Defect in copper excretion to biliary tract

Cu accumulates in liver, causing progressive liver disease and neurologic dx

Sx include liver dx, dysarthria, arthropathy, cardiomyopathy, kidney damage, hypoparathyroidism, Kayser-Fleischer ring around iris of eye

Single missense mutation in 40% of Northern European cases

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7
Q

Hereditary Hemochromatosis

A

Excessive iron absorption in intestine

Accumulates in liver, kidney, heart, joints, pancreas

Common in Northern Europenas, delayed onset (after 40 in men and 60 in women)

Fatigue common, bronzing of skin

Diagnose w/ liver biopsy and hemosiderin staining

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8
Q

Retinoblastoma

A

Autosomal dominant disorder

Tumors form in the retina and fill the eye if untreated

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9
Q

Postaxial polydactyly

A

Autosomal disorder characterized by multiple fingers/toes

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10
Q

Achondroplasia

A

Autosomal dominant disorder characterized by very short limbs

Disease seen in heterozygotes; homozygotes not viable

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11
Q

Albinism

A

Autosomal recessive disorder characterized by the inability to produce melanin from tyrosine

Hypopigmentation of skin, hair

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12
Q

Cystic fibrosis

A

Autosomal recessive disorder

Disrupted chloride transport results in thickened mucus secretions in lungs and the inability of pancreatic secretions to reach the intestine

Chloride sweat test

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13
Q

Delayed age of onset

A

Disorders not evident until adulthood

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14
Q

Reduced penetrance

A

Phenotype is mild or nonexistent in some individuals bc they hae other modifying genes that may affect presentation of this phenotype

Children of these ppl may have much more severe forms of the disease

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15
Q

Variable expression

A

Severity of a disorder depends on expression

Genes can be modified to limit their expression

Expression may be different in offspring

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16
Q

Neurofibromatosis

A

Autosomal dominant disorder w/ variable expression characterized by cafe au lait skin lesions

Some pts get a few lesions; others have large tumors

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17
Q

Pleiotropy

A

Multiple effects from one mutation

Ex. Marfan’s syndrome - defect in fibrillin, leads to multiple effects such as hypermobile joints, incr risk for aortic dissection, displaced lenses in eye, etc.

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18
Q

Allelic Heterogeneity

A

Multiple mutant forms of one type of disorder

Ex. Hb disorders sickle cell anemia and B-thalassemia are caused by dif mutations; have similar effects on pt

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19
Q

Locus heterogeneity

A

Multiple genes affect one pathway

Ex. Urea cycle disorders

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20
Q

Anticipation

A

Dominant disorders are more severe in later generations

Ex. Huntingdon’s disease

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21
Q

Hemophilia A

A

X linked recessive disorder characterized by excessive bleeding due to low levels of factor VIII

Can range from mild to moderate to severe

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22
Q

Duchenne Muscular dystrophy

A

X linked recessive characterized by severe, progressive muscular dystrophy caused by defective dystrophin protein

Show up around age 5 in males; pts confined to wheelchair by age 11

High levels of creatine kinase; Positive Gower’s sign, pseudohypertrophy of calves

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23
Q

Red-Green Colorblindness

A

X linked recessive disorder based on opsin proteins

One red opsin followed by several green opsins genes on X chromosome

Colorblindness caused by unequal crossing over of X chromosomes

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24
Q

Hypophosphatemic rickets

A

X linked dominant disorder

Kidneys cannot reabsorb phosphate, leading to decr ossification of bones (bones are soft, so the bend and distort)

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25
Incontinentia pigmenti
X linked dominant Abnormal skin pigmentation and teeth Only found in females because males w/ this phenotype are not viable
26
Rett syndrome
X linked dominant Autism, ataxia, MR Most males do not make it to term, so it is more freq seen in females
27
Leber Hereditary Optic Neuropathy (LHON)
Mitochondrial inherited disease Optic nerve death in 3rd decade leading to blindness
28
Myoclonic epilepsy w/ ragged red fibers (MERRF)
Mitochondrial inherited disease Epilepsy, ataxia, dementia, myopathy Highly variable expression due to heteroplasmy (some mitochondria may be affected in a cell and others may be normal)
29
Mitochondrial encephalomyopathy and stroke-like episodes (MELAS)
Mitochondrial inherited disease Many stroke like episodes w/ variable expression
30
Fragile X
Most common inherited MR Affects females twice as often as males; shows up in families w/o prior history; normal transmitting males are not likely to be affected but are likely to have unaffected daughters and affected granddaughters because the CGG repeat expands only in female meiosis If repeat gets over 230, then disease is present Long face, prominent jaw, large ears
31
Prader-Willi Syndrome
Genomic imprinting disease caused by deletion of part of the paternal copy of chromosome 15 Characterized by morbid obesity, intellectual defects
32
Angelman Syndrome
Genomic imprinting disease caused by a deletion on part of the maternal copy of chromosome 15 Leads to uncontrollable laughter and puppet-like movements
33
Classic Galactosemia
Missense mutation in gene that codes for GAL-1-P-uridyl transferase, leading to inability to convert galactose to glucose-1-phosphate Causes buildup of galactose, leading to incr synthesis of galactitol, leading to cataracts in infants. Also causes failure to thrive, developmental delay. Screened for at birth
34
Hereditary Fructose intolerance
Defect in fructose 1,6 bisphosphate aldolase Inability to digest fructose; prevalent in 1/20,000
35
Von Gierke Disease
Glycogen storage dx due to defect in glucose-6-phosphatase Results in the inability to utilize broken down glucose, causing hepatomegaly and hypoglycemia
36
PKU
Inability to metabolize Phe, resulting in its buildup Causes defects in myelination, protein synthesis, and eventually MR Dietary restrictions to limit symptoms
37
Maple Syrup Urine Disease
Cannot metabolize branched chain ketoacids from branched chain amino acids Highly prevalent in Menonites of Lancaster County Odor of urine; can lead to death if not accounted for
38
MCAD Deficiency
Deficiency in medium chain acyl coenzyme A dehydrogenase Inability to break down medium chain FA and long chain FA when they are converted into medium chain FA Cause hypoglycemia after fasting due to inability to make ketone bodies; brain needs ketone bodies for energy when blood glucose gets low Tx is to avoid fasting, have a diet high in glucose
39
Congenital Adrenal Hyperplasia
Block in corticoid synthesis (aldosterone, cortisol) Intermediates build up, leading to excess synthesis of androgens Can cause development of male-like sex characteristics in a fetus w/ high androgens May also lead to wt loss, lethargy, dehydration, death Many forms are less severe
40
Zellwegger Syndrome
Severe peroxisome disorder Buildup of toxins leads to neonatal hypotonia, white matter disease, distinctive face, death in infancy Not to be confused with Renee Zellwegger, a condition in which one has the facial similarities of an anteater
41
Mucopolysaccharidoses
Inability to degrade GAGs All are autosomal recessives except Hunter, which is X linked MR occurs in some (Hunter, Hurler, Sanfilippo)
42
Sphingolipidoses
Inability to degrade sphingolipids Gaucher disease occurs mainly in Ashkenazi Jews (B-glucosidase deficiency) Also Tay-Sachs and Niemann-Pick disease are sphingolipidoses
43
I-Cell Disease
Lysosomal storage dx characterized by inability to add mannose-6-P to proteins destined for lysosomes These proteins are instead secreted, and inclusion bodies build up due to defective lysosomes
44
Linkage disequilibrium
Mutations and specific alleles may be inherited together, resulting in a higher than normal frequency of a person with a mutant gene carrying a specific linked allele
45
Genetic association
Some specific allele significantly incr the risk of a person being affected with a particular disease, even though linkage between the two is not known or not a factor
46
FGFR3 Mutations
Cause skeletal dysplasias Most are autosomal dominantly inherited (think about how achondroplasia is inherited)
47
Camptomelic dysplasia
Genetic disorder caused by mutation of SOX9, which is no longer able to activate DAX, thereby preventing testes from properly forming Leads to short limbs and sex reversal
48
Hirshsprung Disease
Enteric neurons do not properly form, so colon cannot move digested material through, causing severe constipation Due to SOX10 mutation
49
Osteogenesis imperfecta
Mutation in glycine residues of a collagen chain disrupts fibril formation, leading to malformed, brittle bones
50
Marfan's syndrome
Fibrillin-1 mutation that results in defective elastin, leadng to abnormal heart and large blood vessels, longer than normal arms and legs, lens dysfunctions, hypermobile joints
51
Junctional epidermolysis bullosa
Defect on laminin that normally anchors cells to ECM Defect results in large blisters on skin due to epithelium being unable to attach
52
HOX genes
Determine anterior/posterior axis development
53
Dorsal/Ventral Axis development
Dorsalized in presence of noggin and choridin Ventralized w/o those two, allowing expression of BMP4
54
Holt-Oram syndrome
TBX5 mutation resulting in thumb and radius defects
55
Ulnar-mammary syndrome
TBX3 mutation, affecting posterior digits and ulna
56
Neurofibromatosis 1
NF1 normally downregulates RAS signaling by hydrolyzing GTP Defect leads to constitutively activated RAS, leading to constant gene activation Appearance of skin lesions called cafe au lait spots are characteristic
57
Li-Fraumeni syndrome
Mutation in p53, resulting in much higher prevalence of various cancers Early age, multiple primary tumors
58
Familial adenomatous polyposis coli
Many polyps, most do not progress to cancer, but some can Due to APC mutation, followed by other defects such as K-Ras activation, p53 mutation, SMAD4 alteration
59
Heridatry non-polyposis colon cancer
Fewer polyps, but they have a much higher chance of developing cancer Due to mutations in DNA mismatch repair genes MSH2 and MLH1
60
BRCA genes
Normally repair double stranded DNA breaks Mutations can lead to a variety of different cancers, mainly breast cancer
61
Liability Distribution
Individuals at one end of the distribution curve are affected
62
Threshold of Liability
Limit that separates normal from affected; may differ by sex or other factor
63
Multifactorial inheritance
More likely to be affected by a disease if you have more affected relatives, if affected relative is of the less affected sex, and if there is an early age of onset for an affected relative
64
Familial Hypercholesterolemia
Quantitative trait w/ autosomal dominant inheritance Accelerates atherosclerosis due to very high blood cholesterol, produces fatty deposits, high risk for CAD and MI, homozygotes severely affected Caused by mutation in LDL receptor
65
Stroke
Multifactorial due to mitochondrial disorder MELAS; mutations in NOTCH3, Protein C and S; Factor V Leiden (hypercoagulability of factor V)
66
Hypertension
Some single gene mutations can cause one symptom: Liddle syndrome due to defective epilthelial Na channel Gordon syndrome due to incr renal salt reabsorption Excess corticosteroid production or renin-angiotensin system mutation
67
Type I Diabetes
Destruction of beta cells of pancreas, leading to decr insulin Shows a genetic component, but also autoimmune Shows association w/ HLA DR3 or DR4
68
Type II Diabetes
High concordance rate in MZ twins Environment plays a large role Recurrence risk is higher if first degree family member is affected
69
MODY
Mature onset diabetes of the young Glucokinase mutations in 50% of cases Also many txn factor mutations that are normally involved w/ pancreatic dvmt or insulin reg
70
Alzheimer's
Risk doubles if first-degree relative is affected Mostly sporadic cleavage of APP precursor can be a gain of fxn mutant, leading to Alzheimer's

Medical Genetics (1 decks)

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