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ROBBINS Flashcards

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1
Q

two most common forms of DNA variations

A

SNPs (single nucleotide polymorphisms) and CNVs (copy number variations)

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2
Q

define : miRNAs

A

microRNA - they do not encode proteins but INHBIT gene expression - involved in post-transcriptional modification

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3
Q

3 categories of human genetic disorders

A
  1. single mutations that produce large effects - AKA mendelian disorder ( high penetrance )
  2. chromosomal disorders
  3. complex multigenic disorders ( low penetrance )
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4
Q

define : polymorphisms

A

variations in genes that are common within a population

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5
Q

define : mutation

A

permanent change in DNA

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6
Q

define : penetrance

A

proportion of individuals with a certain gene mutation that exhibit the clinical symptoms

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7
Q

define : point mutations

A

when one nucleotide base is SUBSTITUTED for another base

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8
Q

define : frameshift mutations

A

INSERTIONS/DELETIONS that can alteration in the reading frame of DNA strand

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9
Q

point mutation that alters the sequence of the encoded protein is AKA

A

missense mutation

can be conservative or non-conservative

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10
Q

point mutation that changes the nucleotide to a stop codon

A

nonsense mutation

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11
Q

if the insertion/deletion mutation is a multiple of 3 then?

A

it CAN’T be a frameshift mutation

-the protein just contains either one more/one less amino acid

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12
Q

*fragile X syndrome

A

type of trinucleotide repeat mutation

CGG on familial mental retardation 1 (FMR1)

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13
Q

which receptor does HIV use to enter cells

A

CCR5

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14
Q

define : codominance

examples?

A

when both of the alleles of a gene contribute to the phenotype
( HLA and blood group )

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15
Q

define : pleiotropic

A

when a single mutant gene leads to many end effects

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16
Q

define : genetic heterogeneity

A

when mutations at several different loci produce the same effect

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17
Q

when an individual inherits the mutant gene but is phenotypically normal

A

incomplete penetrance

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18
Q

when a trait is seen in all individuals carrying the mutant gene but is expressed differently among individuals

A

variable expressivity

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19
Q

do autosomal dominant mutations affect enzyme proteins

A

NO, b/c 50% loss of enzyme activity can be compensate for

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20
Q

what are the two major classes of nonenzyme proteins that are affected by AD disorders

A
  1. enzymes involved in complex metabolic pathways that are subject to feedback inhibition ( ie. LDL )
  2. key structural proteins ( spectrin )
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21
Q

are LOF or GOF mutations more common

A

LOF

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22
Q

AD disorders - nervous system

A

Huntington disease - neurofibromatosis - myotonic dystrophy - tuberous sclerosis

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23
Q

AD disorders - urinary

A

polycystic kidney disease

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24
Q

AD disorders - GI

A

familial polyposis coli

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25
Q

AD disorders - hematopoietic

A

hereditary spherocytosis - von willebrand disease

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26
Q

AD disorders - skeletal

A

marfan syndrome - ehlers danlos - osteogenesis imperfect - achondroplasia

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27
Q
  • characteristics of AR disorders
A
  1. parents are usually unaffected, but siblings show the disease
  2. siblings have 1/4 chance of having the trait
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28
Q
  • characteristics of X-linked disorders
A
  1. affected male parent cant pass onto sons, but all daughters are carriers
  2. sons of heterozygous women have 50% of getting the mutant gene
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29
Q

most metabolic disorders are?

A

AR

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30
Q

X linked - MSK

A

duchenne muscular dystorphy

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31
Q

X linked - blood

A

hemophilia A and B
chronic granulomatous disease
G6PD

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32
Q

X linked - immune

A

agammaglobulinemia

wiskott-aldrich syndrome

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33
Q

X linked - metabolic

A

DI

lesch-nyhan syndrome

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34
Q

X linked - nervous

A

fragile X syndrome

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35
Q

deficient enzyme in GALACTOSEMIA

A

galactose-1-phosphate uridyltransferase

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36
Q

what makes melanin?

A

tyrosine + the enzyme TYROSINASE - results in albinism

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37
Q

the defect in familial hypercholesterolemia

A

reduced function of LDL receptors leads to defective transport of LDL into cells, which causes increased cholesterol production

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38
Q

which drugs can cause severe hemolytic anemia is G6PD patients

A

primaquine

sulfonamides

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39
Q

mode of inheritance of MARFAN syndrome

A

AD

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40
Q

gene deletion product in MARFANs

A

extracellular glycoprotein - fibrillin-1

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41
Q

what is the function of fibrillin

A

fibrillin is a major component of microfibrils which are needed to make elastic fibers

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42
Q

what sites are primarily affected in MARANs

A

elastic tissue - lens of eye, aorta, skeleton

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43
Q

which actual genes are affected in MARFANs

A

FBN1 15q21.1

( FBN2 causes congenital contractural arachnodactyly )

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44
Q

what other factor contributes to MARFANs

A

excessive TGF-Beta production

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45
Q

what ocular feature is seen in MARFAN

A

ectopia lentis - outward and upward dislocation of the lens

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46
Q

*two MC cardiovascular lesions seen in MARFANs

A

MVP and dilation of ascending aorta (MCCOD)

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47
Q

*clinical features in MARFANs

A

mitral regurgitation
tall, with long extremities
double jointed
ectopia lentis

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48
Q

*clinical features if EDS

A

skin is hyperextensible - joints are hypermobile - skin is easily damaged -

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49
Q

MC AR EDS

A

kyphoscoliosis

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50
Q

defect in kyphoscoliosis EDS

A

the enzyme LYSYL HYDROXYLASE - w/o it cant cross link collagen fibers

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51
Q

defect in vascular EDS?

clinical findings?

A

type 3 collagen

thin skin, arterial and uterine rupture (GI!), bruising, small joint hyper-extensibility

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52
Q

EDS type with type 1 collagen defect

A

arthrochalasia

defect is procollagen to collagen

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53
Q

mutation in procollagen-N-peptidase gene causes

A

EDS - dermatosparaxsis type

AR inheritance

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54
Q

EDS classical type defect

A

collagen type 5

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55
Q

which gene is mutated in FAMILIAL HYPERCHOLESTEROLEMIA

A

gene for LDL receptor

56
Q

how is LDL made

A
  1. lives makes VLDL
  2. LPL on capillaries cleaves VLDL to IDL
  3. IDL can either be recycled back to VLDL in the liver or made into cholesterol rich LDL
57
Q

what is the immediate and major source of plasma LDL

A

IDL

58
Q

which apoproteins are on

  1. VLDL
  2. IDL
  3. LDL
A
  1. B-100, ApoE, ApoC
  2. B-100, ApoE
  3. B-100
59
Q

what is needed for cholesterol to exit the lysosomes inside the cell?

A

NPC 1 and NPC2

niemann-pick disease- type C

60
Q
  • which processes are affected by intracellular cholesterol
A
  1. cholesterol suppresses 3-hydroxy-3methylglutaryl coenzyme A (HMG CoA) reductase
  2. cholesterol activates acyl-coenzyme A:cholesterol acyltransferase - which promotes storage of excess cholesterol as esters
  3. suppresses LDL receptor production to prevent excess cholesterol in cell
61
Q

how do statins works

A

inhibit HMG-CoA thus preventing cholesterol synthesis in the cell and increasing the number of LDL receptors as a way to increase the intracellular cholesterol level

62
Q

what are the class mutation is familial hypercholesterolemia ?

A 
class 1 - no synthesis in ER
class 2 - cant get to Golgi
class 3 - defective receptor 
class 4 - normal receptor but cant be internalized
class 5 - internalized but cant be released by endosome so it is degraded
63
Q

lysosomes contain?

what are there properties?

A

hydrolytic enzymes. work in acidic environment and they are SECRETORY enzymes that affect INTRACELLULAR organelles

64
Q

what special modification occur in the Golgi involving lysosomes?

A

a terminal mannose-6-phosphate group is added. this segregates these specific enzymes from the other ones in the Golgi.

65
Q

autophagy vs heterophagy

A

autophagy is lysosomal breakdown of products that originate from INSIDE the cell and while heterophagy originates from OUTSIDE the cell

66
Q

the 5 major classes of LYSOSOMAL STORAGE DISORDERs

A
  1. glycogenosis
  2. sphingolipidoses
  3. sulfatidoses
  4. mucopolysaccharidoses
  5. mucolipidoses
67
Q

type 2 - glycogenosis

enzyme defect and accumulating metabolite

A

POMPE disease

alpha 1,4 - glucosidase (lysosomal glucosidase) - glycogen

68
Q

sphingolipidoses types

A

Gm1 gangliosidosis - type 1 infantile and type 2 juvenile

Gm2 gangliosidosis - TAY-SACHS*, Sandhoff disease

69
Q

enzyme defect and accumulating metabolite in TAY-SACHS disease

A

hexosaminidase A - Gm2 ganglioside

70
Q

enzyme defect and accumulating metabolite in Sandhoff-disease

A

hexosaminidase B - Gm2 ganglioside, globoside

71
Q

enzyme defect and accumulating metabolite in Gm1 gangliosidosis

A

Gm1 ganglioside B-galactosidase - Gm1 ganglioside

72
Q

enzyme defect and accumulating metabolite in METACHROMATIC LEUKODYSTROPHY

A

type of sulfatidoses -

arylsulfatase A - sulfatide

73
Q

enzyme defect and accumulating metabolite in MULTIPLE SULFATASE DEFICIENCY

A

arulsulfatase A,B,C and different sulfatase - sulfatide, steroid suflate, heparin sulfate

74
Q

enzyme defect and accumulating metabolite in KRABBE disease

A

galactosylceramidase - galactocerebroside

75
Q

enzyme defect and accumulating metabolite in FABRY disease

A

alpha-galactosidase A - ceramide trihexoside

76
Q

enzyme defect and accumulating metabolite in GAUCHER disease

A

glucocerebrosidase - glucocerebroside

77
Q

enzyme defect and accumulating metabolite in NIEMANN PICK disease A and B

A

sphingomyelinase - sphingomyelin

78
Q

types of MPSs

A
  1. MPS 1 (hurler)

2. MPS 2 (hunter)

79
Q

enzyme defect and accumulating metabolite in HURLER

A

alpha-L-iduronidase – dermatan sulfate, heparin sulfate

80
Q

enzyme defect and accumulating metabolite in HUNTER

A

L-iduronosulfate sulfatase – dermatan sulfate, heparin sulfate

81
Q

clinical presentation of HUNTER

A

male (X-linked) with aggressive behavior and good vision (NO corneal clouding)

82
Q

clinical presentation of FABRY

A

peripheral neuropathy and CV manifestation

also X-linked

83
Q

morphology of TAY SACHSs

A

neurons are ballooned with vacuoles because of Gm2 ganglioside deposition - stains for oil red O and sudan black B are positive - CHERRY RED SPOT - EM shows lysosomes with WHORLED configuration

84
Q

clinical presentation of TAY SACHs

A

signs being at 6 months - progressive dementia, motor incoordination, muscular flaccidity, blindness
CHERRY RED SPOT +
HEPATOSPLENOMEGALY -

85
Q

NIEMANN PICK disease type A

A

severe infantile form - complete loss of sphingomyelinase - death within first 3 years of life

86
Q

NIEMANN PICK disease type B

A

organomegaly WO CNS manifestations - survive into adulthood

87
Q

clinical manifestation in NIEMANN PICK disease

A

CHERRY RED SPOT +

hepatosplenomegaly +

88
Q

morphology of NIEMANN PICK disease

A

sphingomyelin and fat accumulates in cells ( neurons and hepatocytes ) – lysosomes contain concentric lamellated myelin figures called ZEBRA BODIES - shrunken gyri and widened sulci

89
Q

clinical presentation of NIEMANN PICK type C

A

presents in childhood with ataxia, vertical supranuclear gaze palsy, dystonia, dysarthria, psychomotor regression

90
Q

the MC lysosomal storage disorder

A

GAUCHER disease

91
Q

GAUCHER disease type 1

A

chronic non-neuronopathic form

  • limited to mononuclear phagocytes
  • NO brain involvement
  • spleen and skeleton highly involved
92
Q

GAUCHER disease type 2

A

acute neuronopathic form - infantile acute cerebral pattern

  • NO predilection for jews
  • no glucocerebrosidase activity in tissues
93
Q
  • describe GAUCHER cells
A

distended phagocytic cells that have cytoplasm that looks like CRUMBED PAPER

94
Q

WRIGHT stain used for

A

peripheral blood smear to differentiate between blood cells

95
Q

general clinical features of the MPSs

A
  • coarse facial features, clouding of the cornea, joint stiffness, mental retardation*
  • hepatosplenomegaly, skeletal deformities, valvular lesions, subendothelial arterial deposits
96
Q

basic formation of glucose to glycogen

A
  1. glucose to glucose-6-phosphate via hexokinase (glucokinase)
  2. glucose-6-phosphate to glucose-1-phosphate via phosphoglucomutase
  3. glucose-1-phosphate to uridine disphospoglucose
97
Q

basic breakdown of glycogen

A

glycogen to glucose-1-phosphate until only 4 glucose residues are left – known as limit dextrin , which is further broken down by debranching enzyme

98
Q

glycogen degraded by which enzyme in lysosomes

A

acid maltase ( alpha-glucosidase )

99
Q

define : isochromosome

A

when one arm of the chromosome is deleted and the remaining one is duplicated - either two long arms or two short arms

100
Q

MCC of trisomy

A

meiotic nondisjunction

101
Q

*clinical features of trisomy 21

A

flat facial profile, oblique palpebral fissures, epicanthic folds, congenital heart defects, predisposition to leukemia+neurodegenerative disease+serious infections, gap btw first and 2nd toe,

102
Q

trisomy 18

A

Edwards syndrome

- micrognathia, overlapping fingers, low+misshapen ears, renal malformations, rocker bottom feet

103
Q

trisomy 13

A

Patau syndrome

-cleft lip and palate, microphthalmia, rocker bottom feet, umbilical hernia, cardiac defects

104
Q

22q11 deletions cause

A

digeorge syndrome

+ velocardiofacial syndrome

105
Q

androgen receptor gene

A

on X chromosome (Xq12)

-contains CAG repeats-with shorter repeats, the effects of testosterone is greater.

106
Q

gene important in stature

A

SHOX - deletion leads to short stature (TURNER syndrome)

-excess copy leads to tall stature

107
Q

*clinical features of TURNER syndrome

A

short stature, cystic hygroma in neck leads to webbing, hypothyroidism due to autoantibodies, peripheral edema, CV malformations PREDUCTAL COARCTATION OF AORTA + BICUSPID VALVE, no 2ndary sex characteristics, AMENORRHEA, broad chest

108
Q

MCC of primary amenorrhea

A

TURNER syndrome

109
Q

define : true hermaphrodite

A

implies the presence of both ovarian and testicular tissue

110
Q

define : pseudohermaphrodite

A

disagreement between gonadal sex and phenotypic

111
Q

MC form of male pseudohermaphroditism

A

androgen insensitivity syndrome due to androgen receptor mutation

112
Q

trinucleotide repeats in oogensis

A

fragile x syndrome

113
Q

trinucleotide repeats in spermatogenesis

A

HD

114
Q

trinucleotide repeats in exons vs intron

A

exons-HD

introns- myotonic dystrophy and fragile X

115
Q

repeat in FRAGILE X

A

CGG

116
Q

repeat in FRIEDREICH ATAXIA

A

GAA

117
Q

repeat in MYOTONIC DYSTROPHY

A

CTG

118
Q

repeat in HD

A

CAG

119
Q

repeat in spinocerebellar ataxia

A

CAG

120
Q

2nd MCC of mental retardation

A

fragile X syndrome

121
Q

physical phenotype in FRAGILE X syndrome

A

long face with large mandible, large everted ears, large testicles
-hyperextensible joints, MVP mimics CT disorder

122
Q

most distinctive feature of FRAGILE X

A

macro-orchidism

123
Q

premutations get converted to mutation where

A

oogenesis only

124
Q

mtDNA comes from

A

MOM only

125
Q

human mtDNA codes for

A

37 total genes-
22 for tRNA-
2 for rRNA-
13 for respiratory chain enzymes

126
Q

define : heteroplasmy

A

when you have both wild type and mutant mtDNA

127
Q

prototypical mtDNA disorder

A

leber hereditary optic neuropathy

progressive b/l loss of central vision

128
Q

define : maternal imprinting

A

transcriptional silencing of maternal allele for a gene

129
Q

where does imprinting occur

A

in the sperm or ovum, before fertilization

130
Q

*clinical features of PRADER-WILLI

A

short stature, hypotonia, hyperphagia, obesity, small hands and feet, hypogonadism

131
Q

deletion in PRADER-WILLI

A

paternal chromosome 15q12

the maternal allele is imprinted and therefore inactive

132
Q

deletion in ANGELMANN syndrome

A

maternal chromosome 15q12

the paternal allele is imprinted and therefore inactive

133
Q

*clinical features of ANGELMANN

A

mental retardation, ataxic gait, seizures, inappropriate laughter

134
Q

define : uniparental disomy

A

inheritance of both chromosomes of a pair from one parent

135
Q

define : gonadal mosaicism

A

mutation during embryogenesis of only gonads and not somatic cells
i.e phenotypical normal parent who can transmit disease causing mutation through gametes

136
Q

mutation in CML

A

BCR-ABL

PATHOLOGY | GENETICS (3 decks)

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