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107 terms

USMLE by CJR - Biochem 3

From page 82
STUDY
PLAY
What cell type is visible with Vimentin stain?
Connective tissue
What cell type is visible with Desmin?
Muscle
What cell type is visible with cytokeratin?
Epithelial cells
What cell type is visible with GFAP?
Neuroglia
What cell type is visible with neurofilaments?
Neurons
During the cycle of the Na+/K+ exchanger, what is the status of the pump?
Phosphorylated
What drug inhibits the Sodium pump by binding to the K+ site?
Ouabain
What drugs directly inhibit the Na+/K+ ATPase?
Cardiac glycosides (digoxin, digitoxin)
What result does inhibition of Na+/K+ pump have on Na+/Ca2+ exchange?
Makes it less favorable, so more intracellular calcium, so better contractility
What is the most abundant protein in the human body?
Collagen
What structures does type I collagen make?
Bone, skin, tendon
What disease is caused by defective type I collagen?
Osteogenesis Imperfecta
What structures does type II collagen make?
Cartilage
What structures does type III collaged make?
Vascular stuff, skin, uterus
What is the name for defective type III collagen synthesis?
Ehler-Danlos syndrome
What structures does type IV collagen make?
Basement membrane
What disease is caused by defective type IV collagen production?
Alport syndrome
Where is preprocollagen synthesized?
Rough ER
What type of collagen chains make up preprocollagen?
α chains
What is the pattern of collagen polypeptide?
Gly - X - Y
What are X and Y, usually?
Proline, lysine
What posttranslational modification takes place on collagen in the ER?
Hydroxylation of proline and lysine residues
What cofactor is required for hydroxylation of proline and lysine?
Vitamin C
What other posttranslational modification takes place in the ER?
Glycosylation
What residue is glycosylated?
Hydroxylysine on the pro-α-chain
After glycosylation, procollagen forms. What is the structure of procollagen?
triple helix of 3 α chains
How are the 3 helices held together?
Hydrogen and disulfide bonds
What never forms in osteogenesis imperfecta?
Procollagen
After hydroxylation and glycosylation, what happens to procollagen?
Exocytosis into extracellular space
Once in the extracellular space, what happens to procollagen?
Cleavage of terminal regions (trimming) to form insoluble tropocollagen
Staggered tropocollagen molecules are bound together by bonds between what residues?
Lysine-hydroxylysine
What enzyme catalyzes this reaction?
Lysyl oxidase
What is the end-product of these links?
Collagen fibrils
What is the mode of inheritance of Osteogenesis Imperfecta?
Autosomal Dominant
What is the most commonly defective type of collagen in Osteogenesis Imperfecta?
Type I
Name 4 presenting symptoms of osteogenesis imperfecta
Fractures
Blue sclera
Hearing loss
Dental imperfections (due to lack of dentin)
Type II of osteogenesis has what kind of prognosis?
Usually fatal in utero
A defect in type III collagen causes what 3 symptoms?
Hyperextensible skin
Tendency to bleed
Hypermobile joints
What is the name for this condition?
Ehlers-Danlos
What 3 conditions are associated with Ehlers-Danlos syndrome?
Joint dislocation
Berry aneurysm
Organ rupture
An abnormality of type IV collagen results in what defective structure?
Basement membrane
Abnormalities in the basement membrane causes what symptoms? (3)
Hereditary nephritis
Deafness
Ocular disturbances (sometimes)
What is the name for this condition?
Alport syndrome
What is the mode of inheritance for Alport syndrome?
X-linked recessive
Where is Elastin found?
Lungs
Large arteries
Ligaments
Vocal cords
What two amino acid residues are very common in elastin?
Proline and Glycine
A defect in fibrillin causes what syndrome?
Marfan's
What two conditions can occur as a result in α-1 antitrypsin?
Emphysema
Cirrhosis
What does a Southwestern Blot identify?
DNA-binding proteins
Give an example of codominance
Blood types (A, B, AB)
Give an example of variable expression
2 patients with NF2 have different levels of severity
Give an example of incomplete penetrance
2 people with the gene for a specific disease, only one has symptoms
Give an example of pleiotropy
PKU causes a spectrum of varying symptoms
Give an example of imprinting
Prader-Willi and Angelman's syndrome (depends which parent gives the disease)
Give an example of loss of heterozygosity
Mutation in tumor suppressor gene, complementary allele must be deleted before cancer develops
Give an example of a dominant negative mutation
Nonfunction protein formed by mutation also keeps normal protein from binding
Give an example of locus heterogeneity
Marfan's, MEN2B, homocystinuria, all cause marfinoid habitus.
Define heteroplasmy
Both normal and mutated mtDNA are present, so variable expression in mitochondrial diseases
Define uniparental disomy
Offspring receives 2 copies of a chromosoem from one parent, none from the other
Give the 2 Hardy-Weinberg equations
p squared + 2pq + q squared = 1, and p+q = 1
Hardy-Weinberg theory assumes what 4 things?
1. No mutation at locus
2. No selection for any genotypes at locus
3. No migration
4. Completely random mating
Explain imprinting
One allele is defective, but the other "backup" allele is deleted, so the defect becomes clinically significant
Name a syndrome caused by a deleted paternal allele. Describe the symptoms.
Prader-Willi
Retardation
Hyperphagia
Obesity
Hypogonadism
Hypotonia
Name a syndrome caused by a deleted maternal allele. Describe the symptoms.
Angelmann's syndrome
Retardation
Seizures
Ataxia
inappropriate laughter
In an autosomal recessive disease, what percent of offspring from 2 carrier parents are affected?
25%
In an x-linked recessive disease, what is the likelihood of a son of a heterozygous mother being affected?
50%
Is male-to-male transmission ever seen in x-linked recessive disorders?
Nope
Who can be affected by an x-linked dominant disorder?
Either male or female offspring of mother
ALL female offspring of affected father
Mitochondrial inheritance - who can be affected?
All offspring of affected mothers
Give 3 examples of a mitochondrial linked disorder. What are its symptoms?
Leber's hereditary optic neuropathy (acute loss of central vision)
Myoclonic epilepsy
Mitochondrial encephalopathy

ALL show "ragged red fibers"
Achondroplasia - what factor is defective?
Fibroblast growth factor receptor 3
What is achondroplasia associated with?
Advanced paternal age
ADPKD - unilateral? Bilateral?
ALWAYS bilateral.
ADPKD - Symptoms?
Flank pain
Hematuria
Hypertension
Progressive renal failure
Mutation responsible for ADPKD?
PKD1 on Chromosome 16
ADPKD associations?
Polycystic liver
Berry aneurysms
Mitral valve prolapse
Familial Ademoatous Polyposis - presentation?
Colon covered with adenomatous polyps AFTER PUBERTY.
Mutation responsible for FAP?
Chromosome 5 - APC gene
Pathogenesis of Familial Hypercholesterolemia (IIA)?
Absent or defective LDL receptor
What are the blood cholesterol levels of a heterozygote with Familial Hypercholesterolemia? How about a homozygote?
300 or so
700 or so
Describe the tetrad of symptoms in Osler-Weber-Rendu syndrome (hereditary hemorrhagic telangiectasia)
1. Telangiectasia
2. Recurrent epistaxis
3. Skin discolorations
4. Arteriovenous malformations
What condition is caused by a defect in erythrocyte structural proteins?
Hereditary spherocytosis
What are the names of those proteins?
Spectrin, ankyrin
What are the symptoms of hereditary spherocytosis?
Hemolytic anemia
Increased MCHC
What is the cure for hereditary spherocytosis?
Splenectomy
What two neurotransmitters are decreased in Huntington's disease?
GABA and ACh
What is the trinucleotide repeat in Huntington's disease?
CAG
What chromosome is the Huntington gene located on?
4
What pathologic change occurs in Marfan's syndrome to the aorta?
Cystic medial necrosis
What heart abnormality is found in Marfan's syndrome?
Floppy mitral valve
What ocular defect is found in Marfan's syndrome?
Subluxation of lenses
MEN 2A and 2B are associated with what gene?
the ret gene
Name the 3 findings in neurofibromatosis type I
Cafe' au lait spots
Neural tumors
Lisch nodules
Give the name for Neurofibromatosis type I
von Recklinghausen's disease
What are two other possible symptoms found in Von Recklinghausens' disease?
Scoliosis
Optic pathway gliomas
What chromosome is the locus for the Von Recklinghausen gene?
17 (long arm)
What chromosome is the locus for the Neurofibromatosis type II gene (NF2)?
Chromosome 22
What are the two symptoms of NF2?
Bilateral acoustic schwannomas
Juvenile cataracts
What are the dermatologic symptoms of Tuberous Sclerosis?
Anedoma Sebaceum
"Ash Leaf Spots" on skin (white)
What are the ocular/neurologic symptoms of Tuberous Sclerosis?
Cortical and retinal hamartomas
Seizures
Mental Retardation
Astrocytomas
What are the renal symptoms of Tuberous Sclerosis?
Renal cysts
Renal angiomyolipomas
What are the cardiac symptoms of Tuberous Sclerosis?
Rhabdomyomas
In von Hippel Lindau disease, where are hemangioblastomas usually found?
Retina/cerebellum/medulla
Half of the individuals who have von Hippel-Lindau disease develop carcinomas where?
Kidneys, bilaterally
What gene is deleted in Von Hippel Lindau disease? What is its function?
VHL gene
Tumor suppressor
What chromosome holds the locus for the VHL gene?
3p
Deletion of the VHL gene causes what?
Constitutive expression of HIF (transcription factor)
Activation of angiogenic growth factors