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Flashcards in Biochemistry Deck (293)
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91

alpha-1-antitrypsin, elastase, elastin... relationship?
What if alpha-1-antitrypsin is deficient?

Elastin is broken down by elastase.
alpha-1-antitrypsin inhibits elastase, so inhibits elastin breakdown.
in alpha-1-antitrypsin deficiency: can't inhibit elastase, so get excessive elastase activity and excessive elastin breakdown (can result in panacinal emphysema)

92

Blotting procedures: Southern, Northern, Western, Southwestern

"SNoW DRoP"
Southern Blot --> DNA sample; DNA probe
Northern Blot --> RNA sample; DNA probe
Western Blot --> Protein sample; antibody probe
Southwestern Blot --> identifies DNA-binding proteins, like transcription factors,using labeled oligonucleotide probes

93

sensitivity and specificity of ELISA (enzyme-linked immunosorbent assay)? how does it work/what does it test?

ELISA tests antigen-antibody reactivity; probe pt's blood sample with either:
-test antigen --> to see if immune system recognizes it/if antibody is there
-test antibody --> to see if a certain antigen is there

*solution has a color reaction if positive
*sensitivity and specificity both close to 100%

*Ex of how it works:
1) put antigen to a virus in tube
2) add pt's serum (so, if pt has antibodies to virus, antibodies will bind virus antigens); rinse tube to get rid of unbound antibodies
3) add anti-human Ig that is also connected to an enzyme; these anti-human antibodies will bind the antibody-antigen complexes
4) add a substrate that will cause a color change of the enzyme, it it's bound
***Voila!***

94

Variable expression

severity of phenotype varies from 1 person to another (ie neurofibromatosis type 1, tuberous sclerosis --> may have varying severity)

95

Incomplete penetrance

not all individuals with mutant genotype show mutant phenotype

96

Pleiotropy

1 gene has >1 effect on an individual's phenotype (ie PKU--> lots of seemingly unrelated symptoms)

97

Imprinting

differences in phenotype depend on whether mutation is maternal or paternal origin; occurs due to DNA methylation (ie Prader-Willi and Angelman's syndromes)

98

Loss of heterozygosity

if a patient inherits or develops a mutation in a tumor suppressor gene, the complementary all has to be deleted/mutated before cancer develops (Retinoblastoma)

99

Dominant Negative mutation

a heterozygote produces a non-functional altered protein that also prevents the normal gene product from functioning; exerts a dominant effect (ie nonfunctional factor may bind DNA, thus preventing functional factor from binding)

100

Linkage disequilibrium

tendency for certain alleles at 2 linked loci to occur together more often than expected by chance; measured in a popl

101

Lyonization

random X-inactivation in females

102

Mosaicism

cells in body differ in genetic makeup d/t postfertilization loss of genetic info during mitosis
*germ-line/gonadal mosaic - child has a disease not carried by parent's somatic cells

103

Locus heterogeneity

mutations at different loci can produce same phenotype

104

heteroplasmy

presence of both normal and mutated mitochondrial DNA --> so, have variable expression in mitochondrial inherited disease

105

uniparental disomy

kid gets 2 copies of a chromosome from 1 parent, none from the other

106

Hardy-Weinberg equations and what does the law assume?

p^2 + 2pq + q^2 = 1
p + q = 1
p^2 = freq of homozygosity for p
q^2 = freq of homozygosity for q
2pq = freq of heterozygosity (carrier freq)

if X-linked:
-males = q
-females = q^2

Law assumes:
-no mutation
-no selection
-random matig
-no migration

107

Prader-Willi vs Angelman's syndrome

both due to inactivation or deletion of genes on chromosome 15
-due to imprinting (1 allele is inactive d/t methylation); may also be d/t uniparental disomy
P-W: maternal allele is inactivated; paternal allele should be active but's deleted; mental retardation, hyperphagia, obesity, hypogonadism, hypotonia

Angelman's: inactive paternal allele; maternal allele should be active but is deleted; "happy puppet" --> MR, seizures, ataxia, inappropriate laughter.

108

Mitochondrial myopathies

seen in all offspring of infected mother
-leber's hereditary optic neuropathy (acute loss of central vision)
-myoclonic epilepsy
-mitochondrial encephalopathy
-"ragged red fibers" on micrsocopy

109

Locus heterogeneity

mutations at different loci can produce same phenotype

110

heteroplasmy

presence of both normal and mutated mitochondrial DNA --> so, have variable expression in mitochondrial inherited disease

111

uniparental disomy

kid gets 2 copies of a chromosome from 1 parent, none from the other

112

Hardy-Weinberg equations and what does the law assume?

p^2 + 2pq + q^2 = 1
p + q = 1
p^2 = freq of homozygosity for p
q^2 = freq of homozygosity for q
2pq = freq of heterozygosity (carrier freq)

if X-linked:
-males = q
-females = q^2

Law assumes:
-no mutation
-no selection
-random matig
-no migration

113

Prader-Willi vs Angelman's syndrome

both due to inactivation or deletion of genes on chromosome 15
-due to imprinting (1 allele is inactive d/t methylation); may also be d/t uniparental disomy
P-W: maternal allele is inactivated; paternal allele should be active but's deleted; mental retardation, hyperphagia, obesity, hypogonadism, hypotonia

Angelman's: inactive paternal allele; maternal allele should be active but is deleted; "happy puppet" --> MR, seizures, ataxia, inappropriate laughter.

114

Mitochondrial myopathies

seen in all offspring of infected mother
-leber's hereditary optic neuropathy (acute loss of central vision)
-myoclonic epilepsy
-mitochondrial encephalopathy
-"ragged red fibers" on micrsocopy

115

cell signaling defect of fibroblast growth factor (FGF) Receptor 3

Achondroplasia
-dwarfism, short limbs (but normal head and trunk)
-assoc with advanced paternal age
-autosomal dominant

116

90% of cases are due to mutation in PKD1 (on chrom 16)

ADPKD (autosomal dominant polycystic kidney disease)
-autosomal dominant
-ALWAYS BILATERAL, massive enlargement of kidneys d/t multiple cysts
-flank pain, hematuria, hypertension, progressive renal failure
-assoc with polycystic liver disease, berry aneurysms, mitral valve prolapse

117

Mutations of APC gene on chromosome 5

Familial Adenomatous Polyposis
-autosomal dominant
-colon covered with adenomatous polyps after puberty
-progresses to colon cancer, so have to do colonectomy

118

Elevated LDL d/t defective/absent LDL receptor, tendon xanthomas, atherosclerosis and MI early in life

Familial hypercholesterolemia (hyperlipidemia type IIA)
-autosomal dominant
-heterozygotes: cholesterol approx 300 mg/dL
-homozygotes: cholesterol approx 700 + mg/dL; may develop MI before age 20

119

Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome)

-autosomal dominant, inherited disorder of blood vessels
-telangiectasia, recurrent epistaxis, skin discolorations, arteriovenous malformations

120

spectrin or ankyrin defect

Hereditary spherocytosis
-autosomal dominant
-spheroid RBCs, d/t spectrin or ankyrin defect (responsible for RBC structure)
-hemolytic anemia
-increased MCHC (mean cell hemoglobin concentration)
-dx by osmotic fragility test
-splenectomy = curative