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Pathophysiology I > Genetic Disorders > Flashcards

Genetic Disorders Flashcards

1
Q

what is genetic disease?

A

the price humankind pays for the tendency of genes to change

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2
Q

congenital disorder

A

present/manifest at birth

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3
Q

is congenital disorder genetic?

A

may be genetic or non-genetic (trauma, infection)

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4
Q

when does a genetic disorder manifest?

A

the moment the egg is fertilized (picked the wrong parents ;))

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5
Q

when can genetic disorders manifest?

A

may or may not manifest at birth

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6
Q

examples of genetic diseases that result from post-fertilization somatic mutations

A

can’t be inherited
McCune-Albright syndrome (rare)
Neoplasms (“acquired” genetic disease, common)

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7
Q

hereditary disease

A

“genetic disease” except those you can’t trust

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8
Q

familial disease

A

“diseases that cluster within families”

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9
Q

examples of familial disease

A 
genetic diseases
polygenic disease
nutritional stuff
environmental stuff (lead poisoning)
behavioral stuff (child abuse, obesity)
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10
Q

vertical transmission

A

parent to child (genetic disease)

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11
Q

horizontal transmission

A

within cells of single person (tumors)

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12
Q

what are chromosomal disorders?

A

cytogenic disorders

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13
Q

what causes a chromosomal disorder?

A

wrong number of copies of a chromosome or alterations of one or more chromosomes

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14
Q

what percentage of newborns have a chromosomal disorder?

A

1%

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15
Q

what percentage of chromosomal disorders result in spontaneous abortions?

A

50%

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16
Q

how are chromosomal disorders described?

A

as total chromosomes, sex chromosomes, abnormality

i.e. 47 XY +21; 47 XXY

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17
Q

haploid

A

number of chromosomes in sex cell

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18
Q

diploid

A

exactly twice haploid (i.e. somatic cells)

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19
Q

euploid

A

exact multiples of haploid (2x, 4x, etc.)

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20
Q

aneuploid

A

any other number (45, 47, etc.)

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21
Q

what does aneuploid usually result from?

A

nondisjunction

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22
Q

what is nondisjunction?

A

failure of duplicated chromosomes to separate in meiosis 1
OR
failure of chromatids to separate in meiosis II

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23
Q

what does nondisjunction result in?

A

gametes carrying 2 copies of a chromosome or none

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24
Q

what can also causes nondisjunction?

A

anaphase lag

sister chromatids do not properly separate from each other

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25
Q

what can DNA breaks result from?

A

radiation
chemicals
viral infections

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26
Q

chromosomal disorders mechanisms of action

A

deletion/substitution
inversion
translocation

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27
Q

deletion/substitution

A

terminal or interstitial piece of chromosome deleted/duplicated

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28
Q

inversion

A

broken chromosome segment replaced “backwards”

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29
Q

translocation

A

2 chromosomal breaks with exchange of segments

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30
Q

balanced translocation

A

even exchange of genetic material, no extra or missing DNA

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31
Q

unbalanced translocation

A

unequal exchange, extra or missing genes

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32
Q

robertsonian translocation

A

one large and one extremely small (usually lost) chromosome result

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33
Q

what type of autosomal disorders can cause abortion?

A

autosomal monosomy or no X chromosome causes early abortion

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34
Q

what do trisomies normally produce?

A

infants who will usually die during the first few months of life

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35
Q

exception trisomy that is viable

A

trisomy 21

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36
Q

what can cause autosomal disorders to recur?

A

parent carries a balanced translocation

advanced parental age

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37
Q

what is trisomy 21 also known as?

A

down syndrome

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38
Q

how do you express down syndrome?

A

47XX (or XY) + 21

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39
Q

how does trisomy 21 commonly occur?

A

maternal nondisjunction of 21

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40
Q

what causes maternal nondisjunction of 21?

A

advanced maternal age

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41
Q

what is the most common aneuploidy to reach birth?

A

trisomy 21

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42
Q

what markers indicate trisomy 21?

A

a-fetoprotein
pregnancy-associated protein A
human chorionic gonadotropin

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43
Q

clinical features of trisomy 21

A 
lack of muscle tone at birth ("floppy")
flat face, open, big tongue
slanted eyes and epicanthic folds ("mongolism")
low-set, funny-looking ears
single palmar crease ("simian")
heart defects (40%)
brushfield's spots on iris
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44
Q

trisomy 21 future problems

A 
mental retardation
hypothyroidism
conductive hearing loss
various leukemias
Alzheimer's disease
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45
Q

when do you recognize trisomy 21?

A

usually recognizable at birth

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46
Q

lifespan trisomy 21

A

most die before 30s

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47
Q

what is trisomy 18 known as?

A

edward’s syndrome

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48
Q

how to express edward’s syndrome

A

47XX (or XY) + 18

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49
Q

prevalence edward’s syndrome

A

second most common trisomy to reach term

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50
Q

what causes edward’s syndrome

A

maternal nondisjunction during meiosis II

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51
Q

trisomy 18 prognosis

A

most stillborn or die within first month

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52
Q

trisomy 18 clinical features

A 
growth retardation
prominent occiput
micrognathia
overlapping fingers
rocker-bottom feet
choroid plexus cysts (prenatal US)
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53
Q

sex chromosome disorders-y chromsome

A

necessary and sufficient for phenotypic maleness, assuming the body can also make and use testosterone

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54
Q

sex chromosomal disorders x chromosome characteristics

A

the more X chromosomes, the more abnormal the person

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55
Q

sex chromosomal disoders

A

diagnosis usually missed at birth

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56
Q

what are sex chromosomal disorders better tolerated than?

A

autosomal aneuploidy

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57
Q

example of klinefelter syndrome

A

47XXY, 48XXXY, etc.

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58
Q

what causes klinefelter syndrome

A

maternal (or paternal) (or both) nondisjunction

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59
Q

what slightly increases risk of klinefelter’s

A

advanced maternal age

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60
Q

when is klinefelter syndrome detected?

A

usually detected at puberty

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61
Q

symptoms of klinefelter’s

A 
small testes and penis
long limbs
diminished body hair, rarely go bald
"female" hips
gynecomastia
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62
Q

hormone levels klinefelter’s

A

low plasma testosterone, high estrogen

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63
Q

reproductive ability klinefelter’s

A

almost all are sterile

infertility

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64
Q

IQ klinefelter’s

A

slightly lower IQ’s than XY dudes

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65
Q

what are people with klinefelter’s prone to?

A

osteoporosis

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66
Q

do people with klinefelter’s have a propensity for violent crimes?

A

no!

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67
Q

what can help klinefelter’s?

A

androgen replacement

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68
Q

what is turner syndrome?

A

monosomy of Xp, 45X0

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69
Q

percentage of spontaneous abortions turner syndrome

A

99% spontaneously abort

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70
Q

turner syndrome prevalence

A

most frequent genetic disorder in females (1 in 2000)

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71
Q

when is turner syndrome detected and why?

A

usually detected at puberty, lack feminization

72
Q

symptoms of turner syndrome

A 
nonfunctional ovaries
primary amenorrhea
lack of breast development
no pubic hair
"menopause occurs before menarche"
73
Q

turner physical features

A 
short stature
multiple pigmented nevi
webbed neck
shield-shaped chest
valgus deformity of elbows (turned out)
coarctation of aorta
infertile
74
Q

what can help turner’s syndrome?

A

hGH and estrogen therapy help

75
Q

how is genetic (chromosomal) sex determined?

A

presence/absence of Y chromosome

76
Q

what actually determines intersex states?

A

SRY genes (sex determining region on Y)

77
Q

what happens when dudes have SRY on X?

A

46XX

78
Q

what is gonadal sex determined by?

A

histology of gonads

79
Q

what indicates gonadal sex?

A

follicles vs. tubules vs. both (hermaphrodites) vs. neither (Turner)

80
Q

what determines phenotypic (genital) sex

A

external genitalia

81
Q

what indicates phenotypic sex?

A

vulva vs. penis vs. can’t tell

82
Q

what do true hermaphrodites have?

A

ovaries and testes

83
Q

how to express true hermaphrodites?

A

46XX with translocation of Y to another chromosome-very rare

84
Q

what do pseudohermaphrodites have disparity between?

A

gonadal and phenotypic sex

85
Q

female pseudohermaphrodites

A

penis and ovaries

“penis” is really an enlarged clitoris

86
Q

what causes female pseudohermaphrodites?

A

usually due to error of metabolism

Adrenogenital syndrome

87
Q

male pseudohermaphrodites

A

vulva and testes

88
Q

what causes male pseudohermaphrodites?

A

problems with testosterone synthesis and responsiveness

“testicular feminization”

89
Q

autosomal dominant disorders

A

single gene of a pair affected

90
Q

what do autosomal dominant disorders result in?

A

defective or decreased amounts of protein product

91
Q

what is variable in autosomal dominant disorders?

A

variable penetrance and expressivity

92
Q

when do autosomal dominant disorder manifest?

A

later in life (after carrier has had chance to reproduce)

93
Q

what chance of passing on autosomal dominant disorders?

A

affected parents have 50% chance of passing to offspring regardless of gender

94
Q

mechanisms of autosomal dominant disorders

A

problems with the quantity or arrangement of structural proteins
problems with regulator proteins or receptors
deficiency in proteins that are in short supply even in health
anti-oncogene deletion syndromes
the mutant gene makes a harmful protein (“gain of function”)

95
Q

anti-oncogene deletion syndromes

A

a “second hit” on the normal allele turns it to a tumor cell

96
Q

autosomal dominant disorders-structural proteins

A

Marfan’s syndrome (connective tissue proteins)
Ehlers-Danios (connective tissue proteins)
Hereditary spherocytosis (red cell membrane)
Familial hypertrophic cardiomyopathy (heart muscle proteins)
Familial psoriasis
Achondroplastic dwarfism (fibroblast growth factor receptors)
Hereditary hemorrhagic telangiectasia (several)
Osteogenesis imperfecta (collagen)

97
Q

autosomal dominant disorders-connective tissue proteins

A

Marfan’s syndrome

Ehlers-Danlos

98
Q

autosomal dominant disorders-receptors

A 
Familial hypercholesterolemia (LDL receptor)
Benign familial tremor
Ion channel problems
99
Q

example of ion channel problems autosomal dominant

A

malignant hyperthermia susceptibility syndromes

100
Q

autosomal dominant disorders-short supply proteins

A

von Willebrand’s disease (vWF)
Maturity onset diabetes of the young (glucokinase)
Acute intermittent porphyria

101
Q

autosomal dominant disorders-tumor genes

A 
retinoblastoma
neurofibromatosis I and II
familial polyposis coli
lynch's hereditary non-polyposis colon cancer
multiple endocrine neoplasia syndrome I, Ila, Ilb
Li-fraumeni cancer syndrome
Tuberous sclerosis
Von Hippel-Lindau disease
Peutz-Jegher's syndrome
Adult polycystic kidney disease
102
Q

autosomal dominant disorders-harmful proteins

A

prion diseases
Huntington’s disease (“Huntington’s chorea”)
familial dysplastic nevus syndrome (melanin generates rather than protects from free radicals)
the common thrombophilias (hypercoagulability)

103
Q

examples of the common thrombophillias (hypercoagulability)

A

Antithrombin III deficiency
Protein S deficiency
Protein C deficiency
Factor V Leiden

104
Q

what is Marfan syndrome?

A

heterogenous group of disorders affecting connective tissue matrix

105
Q

Marfan-mutations

A

many different mutations known, many unknown

106
Q

what does Marfan syndrome usually involve?

A

fibrillin I
15q21
associates with elastin fibers

107
Q

what types of manifestations in Marfan syndrome?

A

ocular, cardiovascular and musculoskeletal manifestations

108
Q

Marfan syndrome symptoms

A 
tall, long extremities
long "spider" fingers
hyperextensible "loose" joints
chest wall deformities 
-pectus excavatum or carinatum
spinal curvatures
-kyphosis, scoliosis
funny-looking face
109
Q

Marfan syndrome eye symptoms

A 
ectopia lentis
-lax suspensory ligaments
-virtually pathognomonic
elongated globe, cornea loses convexity
-severe myopia
110
Q

Marfan syndrome heart sx

A 
lax aortic valve ring
-aortic insufficiency
-severe heart failure
"cystic medial necrosis" of thoracic aorta
-aortic dissections
1/3 of Marfan deaths
111
Q

familial hypercholesterolemia

A

most common mendelian disorder
1 in 500 (or less)
many mutations known, usually 19p13

112
Q

what is family hypercholesterolemia characterized by?

A

deficiency or defect in apoprotein B-100 (“LDL”) receptors

-the “bad” serum cholesterol

113
Q

basic mechanism familial hypercholesterolemia

A

decreased liver clearance of LDL from the plasma with high plasma LDL levels
increased receptor-independent uptake of LDL by macrophages
chaotic uptake of LDL by macrophages leads to manifestations

114
Q

familial hypercholesterolemia lab results

A

high serum cholesterol levels 300-500mg/dL

115
Q

xanthomas

A

masses of lipid-stuffed macrophages

116
Q

familial hypercholesterolemia induced precocious atherosclerosis leads to

A

heart attacks

strokes

117
Q

how is familial hypercholesterolemia treated?

A

statins

118
Q

familial hypercholesterolemia homozygotes

A

die in teens

119
Q

autosomal recessive disorders

A

both genes of pair affected

120
Q

what do autosomal recessive disorders result in?

A

absence or lack of function of gene product

121
Q

autosomal recessive penetrance

A

usually complete penetrance

122
Q

when do autosomal recessive disorders manifest?

A

early in life

123
Q

how are autosomal recessive disorders passed on?

A

affected parents always pass gene to offspring regardless of gender

124
Q

what increases risk of autosomal recessive disorders?

A

consanguineous mating increases risk (don’t kiss your cousin)

125
Q

what are autosomal recessive disorders?

A

deficiencies or defects in highly specialized proteins

-enzymes, membrane transport proteins

126
Q

what are autosomal recessive disorders characterized by?

A

hemoglobinopathies

127
Q

what are most inborn errors of metabolism?

A

autosomal recessive

128
Q

what can common disorders often confer?

A

survival advantage to heterozygous carriers

129
Q

examples of survival advantages autosomal recessive disorders

A
  • sickle cell carriers can resist malaria
  • hemochromatosis carriers maintain body iron stores easier
  • cystic fibrosis carriers are resistant to gram-negative intestinal infections
130
Q

autosomal recessive disorders-specialized proteins

A 
albinism
cystic fibrosis
phenylketonuria
galactosemia
maple syrup urine disease
a-1 protease ("antitrypsin") inhibitor deficiency
Wilson's disease
most glycogen storage diseases
most lysosomal storage diseases
131
Q

autosomal recessive disorders-hemoglobinopathies

A

sickle cell anemia
hemoglobin C disease
B-thalassemia major
a-thalassemia syndromes

132
Q

albinism

A

inability to synthesize melanin

133
Q

how many autosomal loci known for albinism?

A

at least 12

134
Q

what deficiency from albinism most common?

A

deficiency of tyrosinase

135
Q

what body parts are affected by albinism?

A

skin, eyes, hair affected

136
Q

light sensitivity-albinism

A

highly photosensitive

137
Q

what are albinos predisposed to?

A

skin and eye cancers

138
Q

what is phenylketonuria a deficiency of?

A

phenylalanine hydroxylase

139
Q

what does an accumulation of phenylalanine cause?

A

CNS toxicity

140
Q

phenylketonuria sx

A

mental retardation
microcephaly
delayed speech development
hypopigmentation

141
Q

phenylketonuria screening

A

all US infants screened at birth

142
Q

what can prevent brain damage with phenylketonuria?

A

dietary restrictions

143
Q

what are lysosomal storage diseases?

A

failure to catabolize large molecules within lysosomes

144
Q

how many lysosomal storage diseases are known?

A

lots

145
Q

what is the prototype lysosomal storage disease?

A

tay-sachs “amaurotic family idiocy”

146
Q

what is tay-sachs a deficiency of?

A

hexosaminidase

147
Q

what builds up in tay-sachs?

A

buildup of GM2 ganglioside (cell membrane component) within lysosomes

148
Q

what is mostly affected in tay-sachs?

A

CNS and retinal neurons

149
Q

what population is tay-sachs common in?

A

Ashkenazic Jews (1 in 30 is a carrier)

150
Q

tay-sachs infants

A

normal at birth

151
Q

what do tay-sach infants develop?

A

mental retardation, blindness, incoordination

152
Q

tay-sachs brain and head sx

A

enlargement of brain and head

-lipid accumulation within neurons

153
Q

tay-sachs macula

A

cherry red spots on macula

surrounding yellow indicates lipid accumulation

154
Q

tay-sachs prognosis

A

death occurs within years

no cure

155
Q

sex-linked disorders

A

little to no homology between X and Y

156
Q

how do defects on one X work sex-linked disorders?

A

defects on one X are overridden by normal allele on other X

-no true x-linked dominant disorders

157
Q

allele requirement sex-linked disorders

A

males (Y) require one abnormal allele (hemizygous), females require two (homozygous)

158
Q

usual genders affected by sex-linked disorders

A

females are carriers

males manifest disease (usually)

159
Q

sex-linked disorders how many males with the gene are affected?

A

all males with the gene are affected

160
Q

when will sex-linked disorders affect a woman?

A

she has two affected x-chromosomes
she suffers from really unfortunate lyonization
disease is expressed when individually lyonized cells are affected (G6PD deficiency)
she has turner’s syndrome (XO) or testicular feminization (XY)

161
Q

are sex-linked disorders transmitted from father to son?

A

never

162
Q

sex-linked daughters of affected males

A

all carriers

163
Q

sex-linked disorders

A 
hemophilia A (factor VIII deficiency)
hemophilia B (factor IX deficiency)
G6PD deficiency ("favism")
Lesh-Nyhan syndrome
Duchenne's muscular dystrophy (Jerry's kids)
Emery-Dreifuss muscular dystrophy
Fragile X syndrome
Fabry's disease
Red-green color-blindness
testicular feminization (common type)
nephrogenic diabetes insipidus
Bruton's agammaglubulinemia
"David the Bubble Boy's" immunodeficiency
164
Q

Lesch-Nyhan Syndrome

A

deficiency of hypoxanthine-guanine phosphoribosyltransferase (HGPRT)
needed for purine synthesis (salvage pathway)
leads to buildup of uric acid (gout)
intellectual disability
writhing movements
self-mutilating behaviors

165
Q

polygenic disorders

A

disorders in which heredity plays a dominant role but there is no single gene

166
Q

what do most cases of polygenic disorders involve?

A

environmental factors

167
Q

polygenic disorders inheritance

A

do not follow clear-cut rules of inheritance

168
Q

how can polygenic disorders represent?

A

congenital or later in life

169
Q

polygenic disorders index patient

A

the sicker the index patient, the greater the risk to close relatives

170
Q

polygenic disorders-siblings

A

the more sibs that are affected, the greater the risk to the next child

171
Q

polygenic disorders-what is tricky to distinguish between?

A

single-gene diseases with incomplete penetrance
genetic diseases modified by environment
genetic heterogeneity

172
Q

polygenic disorders examples

A 
alcoholism
asthma
atherosclerosis
attention-deficit disorder/hyperactivity
baldness and hirsutism
breast cancer risk
cleft palate
diabetes mellitus (type I, type II)
hypertension
pyloric stenosis
schizophrenia
obesity (appetite out-of-sync with bodyweight)
173
Q

acquired genetic disorders

A

a fertilized egg with the disease is non-viable

a post-zygotic mutation involving only some cells occurs

174
Q

expression acquired genetic disorders

A

expression variable depending on what/where affected cells are
McCune-Albright syndrome
Proteus syndrome

175
Q

what is the great acquired genetic disease?

A

neoplasms

Pathophysiology I (10 decks)

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