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2021 Origins > MCQ 3 > Flashcards

MCQ 3 Flashcards

1
Q

What causes Deletion Syndromes?

A
  • usually an error in crossover in meiosis
  • unbalanced exchange of genes
  • one chromosome with duplication; other with deletion
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2
Q

What type of chrome disorder presents with Turner Syndrome?

A

Sex chromosome aneuploidy disorder. Patient has an abnormal number of sex chromosomes

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3
Q

Describe pt population of Turner syndrome?

A

Female with missing X chromosome (XO)

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4
Q

How is Turner Syndrome diagnosed?

A

Karyotype Test

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5
Q

What causes Turner Syndrome?

A

Caused by sperm lacking X chromosome

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6
Q

Describe mosaic Turner syndrome

A
  • Often milder

- some cells have 45 X, but other cells have 46 XX

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7
Q

What causes mosaic Turner Syndrome?

A

Mitotic nondisjunction during post-zygotic cell division

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8
Q

20% of pts w/ Miller-Dieker Syndrome inherit the _______ from a parent who carries__________

A

deletion / a balanced chromosomal rearrangement

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9
Q

Describe the etiology of Miller-Dieker Syndrome

A

contiguous gene deletion syndrome caused by heterozygous deletion of 17p13.3

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10
Q

mechanism responsible for microdeletions

A

recombination at segmental duplication

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11
Q

normal couple has recurrent spontaneous miscarriages. what is the most common cause? What testing will confirm?

A

balanced translocation / standard karyotyping

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12
Q

What is the most likely cause of partial deletion and partial duplication involving the same chromosome?

A

parental chromosomal abnormalities most likely caused pericentric inversion

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13
Q

Where does the Robertsonian translocation usually occur?

A

between chromosome 21q and the long arm of one of the other acrocentric chromosomes (usually chromosome 14 or 22)

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14
Q

-Onset at neonatal to adulthood
-Progressive pulmonary disease
-Exocrine pancreatic insufficiency
-Obstructive azoospermia
-Elevated sweat chloride
concentration
-Growth failure
-Meconium ileus

A

Cystic Fibrosis

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15
Q

Mutation of cystic fibrosis?

A

CFTR Mutation

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16
Q

Sickle cell disease pathogenesis

A 
-Hemoglobin is composed of four
subunits, two α subunits encoded by
HBA on chromosome 16 and two β
subunits encoded by the HBB gene
on chromosome 11
-The Glu6val mutation in β-globin
decreases the solubility of
deoxygenated hemoglobin and
causes it to form a gelatinous
network of stiff fibrous polymers
that distort the red blood cell, giving
it a sickle shape
Glutamate to valine mutation
causing sickled RBCs
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17
Q

Sickle cell disease phenotype

A
  • Onset at childhood
  • Anemia
  • Infarction
  • Asplenia
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18
Q

Sickle Cell

Disease inheritance

A

autosomal recessive

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19
Q

Beta-globin
Glu6Val
Mutation

A

Sickle Cell

Disease

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20
Q

Turner syndrome pathogenesis

A 
Without a second X chromosome,
oocytes in fetuses and neonates with
TS degenerate, and their ovaries
atrophy into streaks of fibrous tissue.
Oocytes can develop but cannot be
maintained
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21
Q

Turner

Syndrome phenotype

A
  • Prenatal onset
  • Short stature
  • Ovarian dysgenesis
  • Sexual immaturity
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22
Q

Female

Monosomy X

A

Turner

Syndrome

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23
Q

Sex
Development
Disorder (46,
XX Male) pathogenesis

A 
-SRY is a DNA-binding protein that
alters chromatin structure by
bending DNA altering gene
expression
-SRY is necessary for the formation
of male genitalia and the absence
forms female genitalia
SRY in females causing male
genitalia
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24
Q

Sex
Development
Disorder (46,
XX Male) phenotype

A

-Prenatal onset
-Sterility
-Reduced secondary sexual features
-Unambiguous genitalia mismatched
to chromosomal sex

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25
Q

Sex
Development
Disorder (46,
XX Male)

A

y-linked or chromosomal

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26
Q

SRY

Translocation

A

Sex
Development
Disorder (46,
XX Male)

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27
Q

Absence of
paternally derived
15q11-
q13

A

Prader-Willi

Syndrome

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28
Q

Prader-Willi

Syndrome inheritance

A

Chromosomal deletion, uniparental

disomy

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29
Q

Prader-Willi

Syndrome phenotype

A
  • Onset at infancy
  • Infantile feeding difficulties
  • Childhood hyperphagia and obesity
  • Hypotonia
  • Cognitive impairment
  • Short stature
  • Dysmorphism
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30
Q

Prader-Willi

Syndrome pathology

A 
-Deletion of 15q11-q13 during
male meiosis gives rise to children
with PWS because children formed
from a sperm carrying the deletion
will be missing genes that are active
only on the paternally derived
15q11-q13.
-The mechanism underlying this
recurrent deletion is illegitimate
recombination between low-copy
repeat sequences flanking the
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31
Q

Miller-Dieker

Syndrome pathology

A 
More than 50 genes have been
mapped within the MDS deletion
region in 17p13.3, but only the
LIS1 gene (MIM 601545) has
been associated with a specific
phenotypic feature of MDS;
heterozygosity for a LIS1
mutation causes lissencephaly
MDS deletion and LIS1 mutation
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32
Q

Miller-Dieker

Syndrome phenotype

A
  • Prenatal onset
  • Lissencephaly type 1 or type 2
  • Facial dysmorphism
  • Severe global intellectual disability
  • Seizures
  • Early death
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33
Q

17p13.3
Heterozygous
Deletion

A

Miller-Dieker

Syndrome

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34
Q

autism pathology

A 
-16p11.2 microdeletion is one of
many microdeletion/
microduplications that recur due to
low-copy repeat sequences (LCRs)
with high sequence homology
flanking the deleted or duplicated
DNA
Microdeletions causing
developmental/intellectual
disability
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35
Q

Autism phenotype

A 
-Onset at birth or first 6 months of
life
-Intellectual disability to normal
intelligence
-Impaired social and communication
skills or frank autism spectrum
disorder
-Minor dysmorphic features
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36
Q

Autism inheritance

A

autosomal dominant or de novo

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37
Q

16p11.2
Deletion
Syndrome

A

Autism

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38
Q

Xeroderma

Pigmentosum pathogenesis

A 
-Caused by mutations affecting the global
genome repair subpathway of nucleotide
excision repair or by mutations affecting postreplication
repair
-Loss of caretaker function required for
maintenance of genome integrity causing
oncogenic mutations
Cancer risk from error with nucleotide
excision repair
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39
Q

Xeroderma

Pigmentosum phenotype

A
  • Onset at childhood
  • UV light sensitivity
  • Skin cancer
  • Neurological dysfunction
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40
Q

Xeroderma

Pigmentosum Inheritance

A

autosomal recessive

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41
Q

Xeroderma

Pigmentosum phenotype

A
  • Onset at childhood
  • UV light sensitivity
  • Skin cancer
  • Neurological dysfunction
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42
Q

Defect of
Nucleotide
Excision Repair

A

Xeroderma

Pigmentosum

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43
Q

Thrombophilia pathogenesis

A

-The coagulation system maintains a delicate
balance of clot formation and inhibition;
however, venous thrombi arise if coagulation
overwhelms the anticoagulant and fibrinolytic
systems
-Impaired Factor V function to accelerate the
conversion of prothrombin to thrombin
-PROC mutation impairing Protein C function
(inactivates Factor V)
Coagulation impaired by errors with
Factor V and PROC function with Protein
C

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44
Q

Thrombophilia phenotype

A
  • Onset at adulthood

- Deep venous thrombosis

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45
Q

Thrombophilia inheritance

A

autosomal dominant

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46
Q

FV and PROC

Mutations

A

Thrombophilia

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47
Q

Retinoblastoma pathogenesis

A

-The retinoblastoma protein (Rb) is a tumor
suppressor that plays an important role in regulating the progression of proliferating
cells through the cell cycle and the exit of
differentiating cells from the cell cycle.
-Retinoblastoma-associated RB1 mutations
occur throughout the coding region and
promoter of the gene
Issue with tumor repressor

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48
Q

Retinoblastoma phenotype

A
  • Onset at childhood
  • Leukocoria
  • Strabismus
  • Visual deterioration
  • Conjunctivitis
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49
Q

Retinoblastoma inheritance

A

autosomal dominant

50
Q

RB1 Mutation

A

Retinoblastoma

51
Q

Neurofibromatosis 1 pathogenesis

A

-NF1 is a large gene (350 kb and 60 exons)
that encodes neurofibromin, a protein widely
expressed in almost all tissues but most
abundantly in the brain, spinal cord, and
peripheral nervous system.
-The clinical manifestations result from a
loss of function of the gene product; 80% of
the mutations cause protein truncation.
Issue with neurofibromin

52
Q

Neurofibromatosis 1 phenotype

A
  • Prenatal onset to late childhood
  • Cafe au lait spots
  • Axillary and inguinal freckling
  • Cutaneous neurofibromas
  • Lisch nodules
  • Plexiform neurofibromas
  • Optic glioma
  • Specific osseous lesions
53
Q

Neurofibromatosis 1 inheritance

A

autosomal dominant

54
Q

NF1 Mutation

A

Neurofibromatosis 1

55
Q

Myoclonic Epilepsy
with Ragged-Red
Fibers pathogenesis

A
  • In MERRF, the activities of complexes I
    and IV are usually most severely reduced.
    -The tRNAs mutations associated with
    MERRF reduce the amount of charged tRNA
    lys in the mitochondria by 50% to 60% and
    thereby decrease the efficiency of translation
    so that at each lysine codon, there is a 26%
    chance of termination.
    -Because complexes I and IV have the most
    components synthesized within the
    mitochondria, they are most severely
    affected.
    Issue with translation at lysine codon
56
Q

Myoclonic Epilepsy
with Ragged-Red
Fibers phenotype

A 
-Onset at childhood through
adulthood
-Myopathy
-Dementia
-Myoclonic seizures
-Ataxia
-Deafness
57
Q

Myoclonic Epilepsy
with Ragged-Red
Fibers inheritance

A

matrilineal, mitochondrial

58
Q

Mitochondrial
tRNA lys
Mutation

A

Myoclonic Epilepsy
with Ragged-Red
Fibers

59
Q

Marfan Syndrome pathogenesis

A

-FBN1 encodes fibrillin 1, an extracellular
matrix glycoprotein with wide distribution. -
Fibrillin 1 polymerizes to form microfibrils in
both elastic and nonelastic tissues, such as the
aortic adventitia, ciliary zonules, and skin.
-Mutations affect fibrillin 1 synthesis,
processing, secretion, polymerization, or
stability
Problem with fibrillin

60
Q

Marfan Syndrome phenotype

A
  • Onset at early childhood
  • Disproportionately tall stature
  • Skeletal anomalies
  • Ectopia lentis
  • Mitral valve prolapse
  • Aortic dilatation and rupture
  • Spontaneous pneumothorax
  • Lumbosacral dural ectasia
61
Q

Marfan Syndrome inheritance

A

autosomal dominant

62
Q

FBN1 Mutation

A

Marfan Syndrome

63
Q

MCAD Deficiency pathogenesis

A 
-MCAD deficiency is caused by homozygous
or compound heterozygous mutations in
ACADM. The point mutation c.985A>G,
which causes an amino acid change from
lysine to glutamate at residue 304
(Lys304Glu) of the mature MCAD protein, is
found in approximately 70% of mutant alleles
of clinically ascertained patients, but
neonatal screening shows over 90 different
loss-of-function mutations to date.
Change from lysine to glutamate in MCAD
protein
64
Q

MCAD Deficiency phenotype

A
  • Onset between 3 and 24 months
  • Hypoketotic hypoglycemia
  • Vomiting
  • Lethargy
  • Hepatic encephalopathy
65
Q

MCAD Deficiency inheritance

A

autosomal recessive

66
Q

ACADM

Mutation

A

MCAD Deficiency

67
Q

Lynch Syndrome pathogenesis

A 
-In most colorectal cancers, including in
familial adenomatous polyposis, the tumor
karyotype becomes progressively more
aneuploid
-Approximately 70% of Lynch syndrome
families with carcinomas exhibiting MSI
have germline mutations in one of four
DNA mismatch repair genes: MSH2,
MSH6, MLH1, or PMS2
Causes tumors and cancer
68
Q

Lynch Syndrome inheritance

A

Autosomal dominant

69
Q

Lynch Syndrome phenotype

A
  • Onset at middle adulthood
  • Colorectal cancer
  • Multiple primary cancers
70
Q

DNA Mismatch
Repair Gene
Mutations

A

Lynch Syndrome

71
Q

Long QT Syndrome inheritance

A

Autosomal dominant

or recessive

72
Q

Long QT Syndrome pathogenesis

A

-Caused by repolarization defects in cardiac
cells
-Most cases of LQT syndrome are caused
by loss-of-function mutations in genes
that encode subunits or regulatory proteins
for potassium channels
Problem with repolarization (K+ channels)

73
Q

Long QT Syndrome phenotype

A 
-QTc prolongation (>470 msec in
males, >480 msec in females)
-Tachyarrhythmias
-Syncopal episodes
-Sudden death
74
Q

Cardiac Ion
Channel Gene
Mutations

A

Long QT Syndrome

75
Q

Pathogenesis of Hypertrophic

Cardiomyopathy

A

Approximately 60% of adult and pediatric patients with a family history of HCM will have a sarcomere mutation identified. In contrast, only approximately 30% of patients without a family history will have positive results, often due to sporadic or
de novo mutations

76
Q

Phenotype of Hypertrophic

Cardiomyopathy

A 
-Onset at adolescence and early
adulthood (age 12 to 21 years)-Left ventricular hypertrophy
-Myocardial crypts or scarring
-Elongated mitral leaflets
-Diastolic dysfunction
-Heart failure
-Sudden death
77
Q

Cardiac

Sarcomere Gene mutation

A

Hypertrophic

Cardiomyopathy

78
Q

Pathogenesis of Hereditary Hemochromatosis

A

-Mutant HFE interferes with hepcidin
signaling, which results in the stimulation of
enterocytes and macrophages to release iron.
The body, therefore, continues to absorb and
recycle iron, despite an iron-overloaded
condition.
Iron overload

79
Q

Phenotype of Hereditary

Hemochromatosis

A 
-Onset at 40-60 years in males and
after menopause in females
-Fatigue, impotence,
hyperpigmentation (bronzing),
diabetes, cirrhosis, cardiomyopathy
-Elevated serum transferrin iron
saturation
-Elevated serum ferritin level
80
Q

HFE Mutation

A

Hereditary

Hemochromatosis

81
Q

Pathogenesis of Fragile X Syndrome

A 
-The FMR1 gene product, FMRP, is
expressed in many cell types but most
abundantly in neurons. The FMRP protein
may chaperone a subclass of mRNAs from
the nucleus to the translational machinery
-More than 99% of FMR1 mutations are
expansions of a (CGG)n repeat sequence in
the 5′ untranslated region of the gene
Problem with FMRP in neurons
82
Q

phenotype of Fragile X Syndrome

A
  • Onset at childhood
  • Intellectual disability
  • Dysmorphic facies
  • Male postpubertal macroorchidism
83
Q

FMR1 Mutation

A

Fragile X Syndrome

84
Q

Pathogenesis of Familial

Hypercholesterolemia

A 
-The LDL receptor, a transmembrane
glycoprotein predominantly expressed in the
liver and adrenal cortex, plays a key role in
cholesterol homeostasis. It binds
apolipoprotein B-100, the sole protein of
LDL, and apolipoprotein E
-Mutations associated with FH occur
throughout LDLR; 2% to 10% are large
insertions, deletions, or rearrangements
mediated by recombination between Alu
repeats within LDLR
Impacts cholesterol homeostasis
85
Q

Phenotype of Familial

Hypercholesterolemia

A 
-Onset for heterozygote: early to
middle adulthood
-Onset for homozygote: childhood
-Hypercholesterolemia
-Atherosclerosis
-Xanthomas
-Arcus corneae
86
Q

Inheritance of Familial

Hypercholesterolemia

A

Autosomal

Dominant

87
Q

Low-density
lipoprotein
(LDLR) Mutation

A

Familial

Hypercholesterolemia

88
Q

Pathogenesis of Duchenne Muscular

Dystrophy (DMD)

A 
DMD encodes dystrophin, an intracellular
protein that is expressed predominantly in
smooth, skeletal, and cardiac muscle as
well as in some brain neurons
-DMD mutations that cause DMD include
large deletions (60% to 65%), large
duplications (5% to 10%), and small
deletions, insertions, or nucleotide changes
(25% to 30%)
Problem with dystrophin in muscle and
neurons
89
Q

Phenotype of Duchenne Muscular

Dystrophy (DMD)

A
  • Onset at childhood
  • Muscle weakness
  • Calf pseudohypertrophy
  • Mild intellectual compromise
  • Elevate serum creatine kinase level
90
Q

Inheritance of Duchenne Muscular

Dystrophy (DMD)

A

X-linked

91
Q

Dystrophin

[DMD] Mutation

A

Duchenne Muscular

Dystrophy (DMD)

92
Q

Inheritance of cystic fibrosis?

A

Autosomal recessive

93
Q

Inheritance of Deafness

A

Autosomal dominant

and recessive

94
Q

Pathogenesis of Deafness

A 
The GJB2 gene encodes connexin 26,
one of a family of proteins that form gap
junctions
-Connexin 26 is highly expressed in the
cochlea, the inner ear organ that
transduces sound waves to electrical
impulses
Impacts gap junctions in ear
95
Q

Deafness

(nonsyndromic) phenotype

A

-Congenital deafness in the
recessive form
-Progressive childhood deafness in
the dominant form

96
Q

GJB2 Mutation

A

Deafness

nonsyndromic

97
Q

Pathogenesis of cystic fibrosis

A

Dysfunction of CFTR can affect many
different organs, particularly those that
secrete mucus, including the upper and
lower respiratory tracts, pancreas, biliary
system, male genitalia, intestine, and sweat
glands
Impacts mucus secretion

98
Q
A

Autosomal recessive

99
Q
A

What is the inheritance type?

100
Q
A

What is the inheritance type?

101
Q
A

What is the inheritance type?

102
Q
A

What is the inheritance type?

103
Q
A

What is the inheritance type?

104
Q
A

What is the inheritance type?

105
Q
A

What is the inheritance type?

106
Q
A

What is the inheritance type?

107
Q
A

What is the inheritance type?

108
Q
A

What is the inheritance type?

109
Q
A

What is the inheritance type?

110
Q
A

What is the inheritance type?

111
Q
A

What is the inheritance type?

112
Q

Difference between x-dominant and x-recessive?

A

X-dominant all females will be affected. In recessive females will not be affected.

113
Q

What is variable expressivity?

A

Variety of expression of one disease within a family.

114
Q
A

Autosomal dominant with reduced penetrance

115
Q
A

Autosomal recessive

116
Q
A

X-linked dominant

117
Q
A

Germline mosaicism: Germline mosaicism means that some sperm or eggs have a gene mutation that may not be present in other tissues of the body

118
Q
A

Autosomal dominant with imprinting

119
Q
A

Digenic: disorder determined by the additive effect of the genotypes at two or more genes from the same parent

120
Q

Imprinting

A

In image all of the sons are passing it down. the affected daughter does not pass it down. Only one parent can pass it down. Father and mother would not both pass it down.

121
Q

How would you rule out a X-linked disorder?

A

If a father passes down the disease to their son.

122
Q

Genetic anticipation

A

A phenomenon in which the signs and symptoms of some genetic conditions tend to become more severe and/or appear at an earlier age as the disorder is passed from one generation to the next.

2021 Origins (7 decks)

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