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Genetic Diseases > Genetic Disease > Flashcards

Genetic Disease Flashcards

1
Q

Xeroderma Pigmentosum

A

Defect in nucleotide excision repair (NER) and cannot repiar pyrimidine dimers A-T.

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2
Q

Cockaynge syndrome

A

defective repair of UV-induced damage in transcriptionally active DNA. Considerable symptomatic overlap with xeroderma pigmentosum.

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3
Q

Retinoblastoma

A

Autosomal Dominant disorder

Tumors of the retina, fill the eye if untreated

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4
Q

Postaxial Polydactyly

A

Autosomal Dominant disorder

Extra digits in hands and feet

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5
Q

Achondroplasia

A

Short Stature, macrocephaly

Autosomal Dominant disorder
Short long bones
Heterozygotes have nearly a normal life-span. Homozygotes die as infants

Etiology: Defect in the Fibroblast Growth Factor Receptor 3 gene. Moderate increse in FGFR3 activity inhibits chondrocyte growth

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6
Q

Albinism

A

Autosomal Recessive

Inability to produce melanin from tyrosine. Patients have hypo-pigmentation in skin and hair

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7
Q

Cystic Fibrosis

A

Autosomal Recessive disorder
Disrupts chloride transport. Affects pancreatic secretions due to clogging of ducts prevent enzymes from reaching lumen of the intestinal tract.
Lungs affected by thickened secretions.

Excessive chloride in sweat

Risk is 1/25, 1/3 that of cousin

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8
Q

Isolated growth hormone disorder (IGHD)

A

Recessive forms make no growth hormone or it doesn’t reach secretion granules. Dominate form, reached granules, binds to normal hormone, disrupts function, dominant negative

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9
Q

Neurofibromatosis

A

Autosomal dominant with variable expression

NF1: neurofibromatosis 1, down-regulates RAS signaling (GTPase activating ability). Dominant gene on chromosome 17. Defect leads to skin lesions, café au lait spots.

Skin lesions called “cafe au lait” spots vary and some get to very large tumors

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10
Q

Marfan Syndrome

A

Deficiency in development of fribrillin (fribillin-1 gene), a scaffolding for deposition of elastin and the assembly of elastic fibers

The syndrome is inherited as a dominant trait, carried by the gene FBN1, which encodes the connective protein fibrillin-1.

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11
Q

Myotonic Dystrophy

A

Autosomal dominant

A trinucleotide repeat disorder

Severity of the genetic disorder worsens in later generations.

It is characterized by wasting of the muscles (muscular dystrophy), cataracts, heart conduction defects, endocrine changes, and myotonia

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12
Q

Huntington’s Disease

A

The disease is caused by an autosomal dominant mutation in either of an individual’s two copies of a gene called Huntingtin, which means any child of an affected person typically has a 50% chance of inheriting the disease. Physical symptoms of Huntington’s disease can begin at any age from infancy to old age, but usually begin between 35 and 44 years of age. Through genetic anticipation, the disease may develop earlier in life in each successive generation.

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13
Q

Hemophilia A

A

Symptoms: Hemorrhages in joints and muscles. Hemarthroses common. Intracranial bleeding was common cause of death before effective therapy.
- Sever form in 50% of patients (less than 1% of activity). Moderate to mild forms exist.

Etiology: X-linked recessive
Deficiency in factor VIII on the X chromosome. Nonesense mutations, deletions, inversion are severe form. Missense mutations are mild form

Genetics:The female will have 50% of the cells making factor VIII and 50% deficient. But 50% is enough to compensate.

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14
Q

Duschenne’s muscular dystrophy

A

Symptoms: Severe, progressive muscular atrophy usually before age 5. Clumsy and weak. In a wheelchair by 11. Heart and respiratory muscles impaired.

Diagnosis: Creatine Kinase can be 20x normal limit.

Etiology: X-linked recessive. Huge gene 2.5 Mb (largest known human gene). Protein binds F-actin and dystroglycan (in membrane) and is in the cytosol. May be involved in cytoskeletal integrity.

Genetics: 1 in 3500 males

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15
Q

Red-green color blindness

A

Symptoms: Dichromatic vision

Etiology: X-linked recessive
Mutation in the Opsin proteins that absorb colors in Cones. Red and green opsins are adjancent on X chromosome. Usually one red followed by one green.

Genetics:

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16
Q

Deuteranopia

A

No green Opsin

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17
Q

Protanopia

A

Disrupted red

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18
Q

Hypophosphatemic Ricketts

A

Symptoms: Abnormal ossification, bones are bent and distort

Etiology: X-linked dominant, Kidneys cannot absorb phosphate

Genetics

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19
Q

Incontnientia Pigmenti

A

Symptoms: Abnormal skin pigmentation and teeth. Neurological and ocular abnormalities.

Etiology: X-linked dominant

Genetics

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20
Q

Rett Syndrome

A

Symptoms: Autism, ataxia, mental retardation

X-linked dominant

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21
Q

Leber Hereditary Optic Neuropathy (LHON)

A

Mitochondrial inherited gene
Optic nerve in 3rd decade. Heteroplasmy is uncommon, pedigrees simple.

Etiology: Missense mutation in protein coding gene

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22
Q

Myoclonic epilepsy with ragged red fibers (MERRF)

A

Singles base changes in a tRNA. Epilepsy ataxia, dementia, myopathy
Heteroplasmic, high variable expression.

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23
Q

Mitochondrial encephalopathy and stroke-like episodes (MELAS)

A

Single-base mutation in tRNA

Heteroplasmic with variable expression

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24
Q

Kearns-Sayre disease

A

Mitochondrial chromosomes disorder

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25
Q

Pearson Syndrome

A

Mitochondrial chromosomes disorder

26
Q

Chronic Progressive external opthamoplegia

A

Mitochondrial chromosomes disorder

27
Q

Fragile X

A

Symptoms: Most common form of mental retardation. Down syndrome be the most common overall. Long face, prominent jaw, large ears. Similar across ethnic groups

Etiology: An increased in triple repeat found in FMR1 gene. Find CGG repeat in 5’ UTR. Abnormal is over 230 copies. At that point no mRNA is made. The large repeats have high methylation. Affects mRNA distribution in neurons, glutamate receptor seems to be key.

Genetics: Display of anticipation. End of long arm of X breaks in low folic acid. Not recessive and not fully dominant. Repeat expands only in female meiosis.

28
Q

Prader Willi

A

Mutation or deletion in the paternal derived chromosome 15.

29
Q

Angelman Syndrome

A

Mutation or deletion in a coding region of the maternally derived chromosome 15.

30
Q

Classic Galactosemia

A

Symptoms: Failure to thrive, Hepatic insufficeincy, cataracts, Developmental delay, In long term, poor growth and mental retardation

Diagnosis: Screening by checking blood for enzyme activity,

Tx: dietary restriction

Cannot convert galactose to glucose efficiently. The Alternate pathways to galactitol and galactonate.

Carbohydrate defect. Galacotse-1-phosphate uridyl transferase. Most same missense mutation in exon 6.

Risk is 1/170, 1/21 that of cousin

31
Q

Galactosemia alternative

A

Defect in UDP-galactose 4 epimerase. Changes UDP-galactose to UDP-glucose.

32
Q

Hereditary Fructose Intolerance

A

Symptoms:

Etiology: Defect in fructose 1,6 bisphosphate aldolase. Normally in liver, kidney, cortex and small intestine

33
Q

Von Gierke Disease

A

Glycogen storage disease. Causes hepatomegaly and hypoglycemia

Etiology: Defect in glucose-6-phosphatase preventing glucose to be released into the liver.

34
Q

Phenylyketonuria (PKU)

A

Hyperphenylalanemias are most widely studied metabolic disorders.

High amounts of phenyalanine disrupts the brain. Disrupts myelination, protein synthesis, and eventually produces retardation.

Treatment: Requires dietary restriction to limit symptoms

Etiology: Phenylalanine hydroxylase gene (PAH)

35
Q

Maple Syrup Urine Disease

A

Symptoms: Accumulation of BCAA (leucine, isoleucine, and valine) and byporducts can lead to neurodegeration and death in months.

Cannot metabolize branched chain ketoacids. 40% of BCAA are branched chain.

Diagnosis: Odor of urine.

Genetics: single missense mutation A-to-G lysine to glutamate. 1 in 7 in the Menonites of Lancaster county.

36
Q

MCAD Deficiency

A

Symptoms: Hypoglycemia after fasting. Present with vomiting and lethargy after minor illness (upper respiratory, gastroenteritis). Fatty acid intermediates accumulate, insufficient ketone bodies, glycogen gone. Not converting to ketone bodies for export to other tissues, including BRAIN!!

Treatment: Provide supportive care during episodes. Provide usable calories promptly (glucose). Avoid fasting

Etiology: Median-chain acyl-coenzyme A dehydrogenase.
Most common fatty acid metabolism defect.
Episodic hypoglycemia after fasting.

37
Q

Congenital Adrenal Hyperplasia (CAH)

A

Block in corticosteroid synthesis.

Excess precursors can be androgenix or converted to weak androgens.

Virilization of females in utero.

Severe forms cause salt-wasting (weight loss, lethargy, dehydration, death)

38
Q

Zellwegger Syndrome

A

Most severe peroxisome biogenesis disorder.

Neonatal hypotonia, pregressive white matter disease, distinctive face, death in infancy.

Etiology: Mutations in proteins needed for peroxisome biogenesis and importing proteins into matrix.

39
Q

Lysosomal Storage Disorder

A

Lysosomes degrade many materials including mucopolysaccharides (glycoaminoglycans), sphingolipids and glycoproteins and glycolipids.

Accumulate in cell causing cell, tissue and organ dysfunction.

40
Q

Mucopolysaccharidoses

A

Lysosomal enzyme deficiency

Reduced degradation of glycoaminoglycans (heparan sulfate, dermatan sulfate, keratan sulfate, chondroitin sulfate)

41
Q

Hunter MPS

A

X-linked
Mucopolysaccharide deficiency
Mental retardation

42
Q

Hurler MPS

A

Growth deficiency, Coarse facies. Facial features become more distorted with age

Autosomal recessive.

More severe than Scheie. Defect in the a-L-iduronidase
Mental retardation

43
Q

Scheie MPS

A

Defect in a-Liduronidase. Less severe than Hurler (which has the same defect)

44
Q

Sanfilippo MPS

A

Autosomal Lysosomal disease with the inability to break down mucopolysacchrides

45
Q

Sphingolipidoses

A

Mucolipidoses (sphnigolipi degradation is deficient)

several well known type: Gaucher (beta-glucosidase deficiency) –>Ashkenazi JEws
Tay-Sachs Beta-hexosaminidase A deficiency
Niemann-Pick, sphingomyelinase deficiency

46
Q

I-cell Disease

A

Related to Mucolipidosis II (MLS II) is not a specific lysosomal enzyme defect. Lysosomal enzymes traget to lysosome by having mannose-6-phosphate and lysosomal receptor. In I-cell the phosphotransferase is deficient. Many of the enzymes to not make it to lysosome and thus a accumulation of products appear as inclusions, hence name I-cell for Inclusion cell

47
Q

OTC deficiency

A

Urea cycle enzyme deficiency used to combine carbomoly phosphate with ornithine to shuttle across the mitochondrial membrane to the cytosol.

X-linked. Women can be symptomatic carriers.

Tx: need sufficient calories and protein for normal growth and development. Prevent hyperammonemia from excess nitrogen

48
Q

Cystinuria

A

Cystine is 2 cysteines with disulfide bond.

Deficient transporter for dibasic amino acids prevents reabsorption and cause high levels in urine.

Cystine is least soluble of amino acids that can form kidney stones.

Solubilize cystine with water, high pH and penicillamine.

49
Q

Cystinosis

A

Defective transporter for lysosomes, cystine crystals in them

50
Q

Wilson’s Disease

A 
Symptoms: Acute or chronic liver disease.  
-Dysarthria, diminished coordination
-Arthropathy, cardiomyopathy
-Kidney damage, hypoparathyroidism
Kayser-Fleischer ring in eye

Etiology: Metal ion transporter deficiency in copper; defect in gene ATP7B (predominantly expressed in liver and kidney). Defect in the copper excretion to biliary tract. Accumulates in liver, progressive liver disease and neurological abnormalities.

51
Q

Hereditary Hemochromatosis

A

Symptoms: Fatigue common, varies considerably. Joint pain, diminished labido, diabetes, increase skin pigmientation, cardiomyopathy, liver enlargement and cirrhosis.

Diagnosis: Liver biopsy with hemosiderin staining

Treatment: Reduce iron

Etiology:Excessive iron absorption in the intestine.
Accumulates in liver, kidney, heart, joints, and pancreas.

Genetics: Linkage to HLA region. Class I-like gene called HFE. Binds transferrin receptor on cell surface and inhibits iron uptake in cells and affects the sensor for iron in intestine. This causes the brush border uptake of iron to increase with no feedback.

Another common mutation is in C282Y, cysteine to tyrosine. The Cysteine being important for a disulfide bond. The prevelance suggests that it is selectively advantageous in areas where iron deficiency is common. 1 in 200 to 400 affected. Incomplete penetrance (some who carry gene will not express the phenotype). Delayed onset. Common in Nothern Europeans

52
Q

Anylosing spondylitis

Which allele?

A

HLA-B27. People with B27 are 90x more likely than other to have ankylosing spondylitis

Ossification of spinakl discs, joints and ligaments. Likely an autoimmune disorder

53
Q

Hypochondroplasia

A

defect in FGR3 but less than achondromplasia in terms of receptor activation

54
Q

Thanatophoric dysplasia

A

Severe form of achondroplasia that is essentially lethal, very short limbs, highly activated receptor

55
Q

Camptomelic dysplasia

A

Mutation in SOX9. Short limbs, sex-reversal of XY fetuses

56
Q

Hirschsprung (HSCR) disease

A

Neural crest defect causing enteric neurons not develop properly. Colon hypomobility, severe constipation. 4 times as many males affected.

SOX10 (a High mobility group HMG family transcription factor)

57
Q

Osteogenesis Imperfecta

A

Collagen is highly modified with proline and glycine. Mutations in glycines disrupt fibril formation. Bone formation is disrupted, mild to leathal forms

58
Q

Junctional Epidermolysis Bullosa

A

Epithelia not attach, large blisters form on skin due to mutation in LAMC2 (the laminin gene important in anchoring cells to ECM)

59
Q

Holoprosencephaly

A

Defect in the SHH mutation. SHH attaches to cholesterol in membrane necessary for proper cell patterning (paracrine signally)

60
Q

Holt-ORam Syndrome

A

Thumb radius defects most common. T-box gene TBX mutated

61
Q

Ulnar-mammary syndrome

A

Posterior defects such as posterior digits, ulna (most affected)

Genetic Diseases (2 decks)

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