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Pathology > Genetic Disorders Part 1 > Flashcards

Genetic Disorders Part 1 Flashcards

1
Q

what is genetics

A
  • study of heredity

- study of function and composition of a single gene

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2
Q

what is genomics

A

study of ALL GENES and their relationships to identify their combined influence on and development of the organism

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3
Q

what are hereditary disorders

A

derived from the parents = familial

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4
Q

define congenital

A

-present at birth

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5
Q

does congenital imply heredity

A

no!

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6
Q

nature of genetic abnormalities contributing to human disease

A
  1. mutations in protein-coding genes

2. alterations in protein-coding genes other than mutations

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7
Q

what are mutations

A

permanent change in DNA

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8
Q

mutations of germ cells are transmitted to who

A

progeny

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9
Q

mutations of germ cells may give rise to what type of diseases

A

inherited disease

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10
Q

are mutations of somatic cells transmitted to progeny

A

no!

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11
Q

mutations of somatic cells cause

A
  • cancer

- congenital malformations

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12
Q

what mutations can occur in protein-coding genes

A
  1. point mutations
  2. frameshift mutations
  3. trinucleotide repeat mutations
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13
Q

name 2 point mutations

A
  • missence mutations

- nonsense mutations

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14
Q

what are missence mutations

A

change in SINGLE nucleotide base

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15
Q

example of a missence mutation

A

sickle cell disease

A–>T

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16
Q

what are nonsense mutations

A

termination codon; interrupt translation

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17
Q

what are the termination codons

A

UAA
UAG
UGA

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18
Q

what are frameshift mutations

A
  • deletion and insertion
  • one or 2 base pairs
  • reading frame is altered
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19
Q

what are trinucleotide repeat mutations

A

-amplification sequence of 3 nucleotides

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20
Q

example of trinucleotide repeat mutations

A

Fragile X syndrome

CGG amplification

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21
Q

what are other alternations in protein-coding genes oter than mutations

A
  1. polymorphisms
  2. epigenetic changes
  3. alternations in non-coding RNAs
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22
Q

what are 2 most common types of polymorphism

A
  • single nucleotide polymorphism (SNP)

- copy number variation (CNV)

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23
Q

what are single nucleotide polymorphism (SNP)

A
  • variation at a single nucleotide position

- anywhere in the genome

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24
Q

1% of SNP occurs in

A

coding regions therefore alters gene product

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25
Q

are SNPs inherited

A

coinherited with a disease

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26
Q

what are copy number variations (CNVs)

A

large stretches of DNA

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27
Q

what % of CNSs are involved with gene-coding sequences

A

50%

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28
Q

CNVs contribute to

A

human phenotypic diversity

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29
Q

CNVs affect

A

CNS and immune system! (EXAM)

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30
Q

what are epigenetic changes

A
  • modulation of gene

- absence of mutation

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31
Q

how can epigenetic changes occur

A
  • methylation of gene promoter
  • silencing of tumor suppressor gene
  • acetylation of histone
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32
Q

what is imprinting

A

physiologic epigenetic silencing (gene in that particular chromosome is silent or not expressed)

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33
Q

name 2 alternations in non-coding RNAs

A
  1. microRNA

2. long non-coding RNA

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34
Q

what do long non-coding RNA do

A
  • do not encode protein

- inhibit translation

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35
Q

what are the 3 major categories of genetic disorders

A
  1. mendelian disorders: disease caused by single-gene defects
  2. complex multigenic disorders
  3. cytogenetic disorders
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36
Q

what are the transmission patterns of single gene Mendelian disorders

A
  1. autosomal dominant
  2. autosomal recessive
  3. X-linked
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37
Q

what are the characteristics of an autosomal dominant gene

A
  • heterozygous state
  • at least 1 parent is affected
  • M an F are affected
  • 1 chance in 2 (50%) **
  • delayed age at onset
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38
Q

example of an autosomal dominant disease

A

Huntington disease (mutation at birth, but doesn’t manifest until adult)

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39
Q

do autosomal dominant genes encode enzymes

A

NO!

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40
Q

autosomal dominant genes are involved in

A
  1. regulation of metabolic pathways (eg. Familial Hypercholesterolemia)
  2. structural proteins (eg. collagen), cytoskeletal components (eg. ankyrin)
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41
Q

clinical features of autosomal dominant inheritance are affected by

A
  • variable expressivity

- reduced penetrance

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42
Q

what type of disease is Familial Hypercholesterolemia

A

an autosomal dominant inheritance

1 in 500 affected

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43
Q

what does Familial Hypercholesterolemia effect

A

intracellular transport of LDL

catabolism of LDL

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44
Q

where is the mutation in Familial Hypercholesterolemia

A

in LDL receptor

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45
Q

what class of Familial Hypercholesterolemia is most common

A

class II

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46
Q

what is class II Familial Hypercholesterolemia

A

defective folding of protein

  • receptor is present
  • impaired transport of LDL
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47
Q

what are the clinical manifestations of Familial Hypercholesterolemia

A
  • atherosclerosis
  • coronary artery disease
  • xanthoma
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48
Q

what type of disease is Marfan syndrome

A

autosomal dominant

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49
Q

Marfan syndrome affects what gene

A

FBN1 gene

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50
Q

characteristics of marfan syndrome

A
  • affects structural protein fibrins
  • skeletal abnormalities
  • ecotopia lentis
  • CHF
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51
Q

what is the most common cause of death in Marfan syndrome

A

aortic rupture

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52
Q

Marfan syndrome results in a loss of

A

microfibrils

  • excessive activation of TGF-beta
  • affects vascular smooth muscle
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53
Q

what drugs are used to treat Marfan syndrome

A

-angiotension receptor blockers (ARBs) may improve cardiac function in MFS

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54
Q

what tyep of disease is Ehlers-Danlos syndrome

A

autosomal dominant

55
Q

what are the 3 types of Ehlers-Danlos Syndrome

A
  1. Classic EDS
  2. Vascular EDS
  3. Kyphoscoliotic EDS
56
Q

what is the mutation in classic EDS

A

-COL5A1 and COL5A2 (type V collagen defect)

57
Q

what is the mutation in vascular EDS

A

-COL3A1 gene (type III collagen defect)

58
Q

what is the mutation in Kyphoscoliotic EDS

A
  • deficient enzyme: Lysyl hydroxylase

- type I and III colagen

59
Q

EDS causes the skin to be

A

hyperextensible

  • vulnerable to trauma
  • poor wound healing
60
Q

EDS also affects

A
  • cornea
  • blood vessels
  • colon may rupture
61
Q

characteristics of autosomal recessive inheritance disorders

A
  • both alleles are mutant
  • trait does not affect parents
  • 25% recurrence risk
  • low frequency mutant gene = strong likelihood of consagunitiy (related by blood)
  • uniform expression
  • complete penetrance
  • early in life
  • new mutations rarely detected
62
Q

do autosomal recessive disorders affect enzymes

A

yes! enzyme proteins are affected

63
Q

what is the mutation in cystic fibrosis

A

mutation in CFTR (cystic fibrosis transmembrane conductance regulator gene)

64
Q

what is the most common cystic fibrosis mutation

A

change in F508

65
Q

what are complications of CF in pancreas

A
  • pancreatitis
  • hyperglycemia
  • biliary atresia
  • neonatal obstructive jaundice
  • cholelithiasis
  • Vit. deficiency
  • Meconium Ileus
66
Q

complication os CF in lungs

A
  • pneumonia
  • bronchiectasis
  • lung abscess (S. aureus, P.aeru, H.influ_
  • Sinusitis
  • mucoid impaction
  • nasal polyps
  • respiratory failure
67
Q

what are other complications of CF

A
  • congenital bilateral atrophy of vas deferens (CBAVD)
  • infertility
  • strictures in the colon
68
Q

how can CF be diagnosed

A
  • quantitive sweat test

- CFTR mutation lab evidence

69
Q

what factors can give a false positive or negative sweat test

A

false positive: eczema, Klftr

false negative: hyponatremia, malnutrition

70
Q

how is CF treatment managed

A
  • team approach

- supportive

71
Q

who does Phenylketonuria affect

A

Scandinavian

72
Q

what is phenylketonuria

A

phenylalanine hydroxylase deficiency

73
Q

what is hyperphenylalainemia

A
  • normal levels at birth
  • few weeks: plasma levels increase
  • 6mo: mental retardation
  • seizures, eczema
74
Q

what are maternal PKU syndrome

A
  • heterozygous infant
  • microcephaly
  • mental retardation
  • congential heart disease
75
Q

what type of disease is galactosemia

A

an autosome recessive

76
Q

galactosemia affects what gene

A

galactose -1-phosphate uridyl transferase (GALT)

77
Q

galactosemia affects what part of the body

A
  • brain
  • eyes
  • liver
  • spleen
  • kidneys
78
Q

in newborns, galactosemia causes

A
  • vomiting
  • diarrhea
  • jaundice
  • hepatomegaly
79
Q

what type of disease is a lysosomal storage disease

A

autosomal recessive

80
Q

who does lysosomal storage affect

A

infants, children

81
Q

what is mutated in lysosomal storage disease

A
  • gene that codes for specific enzymes
  • therefore lack of specific enzymes
  • mononuclear phagocytes
82
Q

Tay-Sachs disease affects

A

Ashkenazi Jews

83
Q

tay-sachs disease is deficient in

A

hexosaminidase A

84
Q

describe the progression of Tay-Sachs disease

A

at birth: normal
3-6 mo: motor weakness
2-3 yrs: progressive disease; death

85
Q

Tay-Sachs disease affects

A

brain, spinal cord, retina

86
Q

under a microscop Tay-Sachs is characterized by

A
  • neuron, with lipid vacuolation

- lysosomes with whorled configuration

87
Q

Tay-sachs disease has a mutation in what gene

A

HEXA

88
Q

how can you diagnose the mutation in HEXA gene

A
  • plasma levels or WBS
  • prenatal Dx: CV sampling, amnioscentesis
  • carriers: genotyping
89
Q

what is characteristic of a mutation in HEXA gene

A

retina: cherry red spot

90
Q

Niemann-pick disease (NPD) affects

A

Ashkenazi Jews

91
Q

NPD is deficient in what

A

acid sphingomyelinase

92
Q

what is type A NPD

A

neurodegenerative

  • results in organomegaly
  • fatal in 3 yrs
93
Q

what is type B NPD

A

no CNS involvement
+ organomegaly
survival to adulthood

94
Q

what microscopic features are characteristic of NPD

A

vacuolated hepatocytes and Kupffer cells with accumulated sphingomyelin

95
Q

what genes are affected in type C NPD

A

NPC1 and NPC2

96
Q

type C NPD is defective in

A

intracellular cholesterol/lipid transport

97
Q

type C NPD causes

A

ataxia, dystonia

-vertical supranuclear gaze palsy

98
Q

what type of disease is Gaucher disease

A

autosomal recessive

99
Q

what enzyme is Gaucher disease deficient in

A

glucocerebrosidase

100
Q

what type of Gaucher Disease is most comon

A

type 1

101
Q

what does Gaucher disease affect

A

Ashkenazi Jews

102
Q

what symptoms does Gaucher disease cause

A
  • osteopenia (radiographic bone disease; Erhlenmyer flask deformity)
  • hepatosplenomegaly
103
Q

is Gaucher disease neuronopathic

A

no; no CNS manifestation

104
Q

what is type II Gaucher disease

A

acute infantile

  • cause seizures
  • incompatible with life
105
Q

what is type III Gaucher disease

A
  • chronic neuronopathic
  • causes mental retardation
  • seizures
106
Q

what is the pathogenesis of Gaucher disease

A
  • senescent RBC release glycosphingolipids

- degraded in spleen liver, bone marrow

107
Q

function of glucocerebrosidase

A

cleaves glucose from ceramide

108
Q

what happens in a glucocerebrosidase deficiency

A

-glycosphingolipids accumulate

109
Q

what cytokines are activated in glucocerebrosidase deficiency

A

IL-1, IL-6, TNF

110
Q

what microscopic features are characteristic of Gaucher disease

A
  • lipid laded Gaucher cells in bone marrow

- Gaucher cell with distended lysosome

111
Q

what therapy is given for Gaucher disease

A
  • IV recombinant glucocerebrosidase for life
  • oral drugs that inhibit glucocerebroside synthase
  • gene therapy - normal gene transfected autologous hematopoietic stem cells (HPC)
112
Q

what accumulates of Mucopolysaccharidoses (MPS)

A
  • dermatan
  • heparan
  • keratan
  • chondroitin sulfate
113
Q

what are the symptoms of mucopolysaccharidoses

A
  • skeletal abnormalities
  • hepatomegaly
  • cardiovascular disease
114
Q

what is Hurler Syndrome

A

MPS Type 1

115
Q

MPS type 1 is deficinet in

A

L-iduronidase

116
Q

what is the life expectancy of MPS type 1

A

6-10yrs

117
Q

what enzymes build up in MPS type 1

A
  • dermatan

- heparan

118
Q

what are the effects of MPS type 1

A
  • mental retardation

- affects vascular endothelium, neurons, cornea

119
Q

what is Hunter syndrome

A

MPS type II

120
Q

what type of disease is MPS type II

A

X-linked!

all other MPS = autosomal recessive

121
Q

what enzyme is deficient in MPS type II

A

L-iduronate sulfatase

122
Q

what is the clinical corse of MPS type II

A

MILD

123
Q

what is affects is absent in MPS type II

A

corneal clouding

124
Q

what type of disease is glycogen storage disease (glycogenoses)

A

autosomal recessive inheritance

125
Q

what are the 3 forms of glycogen storage disease

A

hepatic, myopathic, miscellaneous

126
Q

describe the hepatic form of glycogen storage disease

A
  • organomegaly
  • hypoglycemia
  • Von Gierke = type 1
  • glucose 6 phosphatase
127
Q

describe the myopathic form of glycogen storage disease

A 
McArdle disease =Type V
Muscle phosporylase
Skeletal muscle only
Painful cramps
Myoglobinuria
Onset: 20 y.o.
128
Q

describe the miscellaneous glycogen storage disease

A 
Pompe disease = Type II
Generalized glycogenosis
Lysosomal glucosidase 
     (acid maltase)
Hepatomegaly: mild
Massive CARDIOMEGALY
129
Q

all sex linked disorders are

A

x-linked

130
Q

what are the characteristics of x-linked disorders

A
  • heterozygous female carriers transmit only to sons
  • rarely express phenotypic change
  • sons: 1 chance in 2 of receiving mutant gene from heterozygous mother
  • son manifest the disease
131
Q

in x-linked disorders affect males do not transmit disorder to

A
  • sons

- all daughters are carriers

132
Q

what are the 3 most common X-linked recessive inheritance

A
  • hemophilia A
  • Duchenne/Becker muscular dystrophy
  • Fragile X syndrome
133
Q

what type of disease is hemophilia A

A

x-linked

134
Q

what gene is mutation in hemophilia A

A

F8 gene

-results in inversion of 22 sequence (40%)

Pathology (18 decks)

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