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Genetics Flashcards

1
Q

What is the FISH study and what is it used for?

A

Synthesis of a single-stranded DNA primer that is complementary to the sequence of interest, tagged with fluorescent marker–> visible using UV light

Used to identify presence/absence of a specific sequence in a cell

Available for: Tri 13/18/21, Prader-Willi, Angelman, Cri-du-chat, DiGeorge, Miller-Dieker, Williams, 4p deletion

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2
Q

What is mass spectroscopy and what is it used for?

A

Detection of very small differences in mass of PCR products because of variations in DNA sequence

Done prenatally or postnatally

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3
Q

What is a microarray and what is it used for?

A

Molecular fragments of DNA/protein attached to a glass or plastic slide in a specific order

Uses:
1. Comparative Genomic Hybridization (CHG) microarray: attempts to identify number of copies of a particular gene- determine loss/gain
2. Microarray expression analysis: determine over/under-expression
3. Mutation microarray analysis: identify mutations/polymorphisms

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4
Q

What is methylation analysis used for?

A

Detection of imprinting disorder.

Ex. Beckwith-Wiedemann syndrome

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5
Q

What is whole EXOME sequencing?

A

Determines nucleotide sequence of all protein coding sites (exomes)

*Useful if patient without a clear reason for specific phenotype

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6
Q

What is whole GENOME sequencing?

A

Sequences entire genome- introns and exons

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7
Q

Most common single-gene disorder in Caucasian population/life-shortening inherited disease

A

Cystic fibrosis
Autosomal recessive (nonsense mutation)

CFTR= cAMP regulated chloride channel, regulator of other Na/Cl channels

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8
Q

Characteristics of autosomal dominant disorders

A
  1. Each disease is rare in the population
  2. 1/200 people
  3. Wide variation of expression with vertical transmission
  4. NO SKIPPED GENERATIONS
  5. Male = Female (equally likely to transmit to offspring)
  6. Father to son transmission observed
  7. Recurrence risk: one carrier parents 50%, both parents affects 75%

Ex. spherocytosis, Waardenberg syndrome

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9
Q

Characteristics of autosomal recessive disorders

A
  1. RARE in population
  2. Less variation in expression
  3. Clustering of disease among siblings but not usually parents
  4. Male = Female (equally likely to transmit to offspring)
  5. Recurrence risk:
    - 2 carrier parents 25%
    - affected parent homozygous with unaffected parent= ALL offspring carriers
    - affected parent homozygous with carrier 50%
    - carrier parent mates with unaffected parent: NO offspring affects, 50% chance carrier
    - 2x carrier parent: 25% affected, 50% carrier, 25% unaffected
    - 2x affected parent: 100%

Ex. cystic fibrosis, majority of inborn errors of metabolism

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10
Q

What is the Lyon Hypothesis?

A

One X chromosome in each female cell is inactivated randomly early in embryonic development and cannot be reactivated–> becomes Barr body
Unequal # of X-linked genes in males/females
Females have 2 population of cells (X paternal, X maternal)
Males= no Barr bodies
Turners= no Barr bodies

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11
Q

Characteristics of X-linked recessive disorders

A
  1. Usually clinically evident in MALES
  2. SKIPS GENERATIONS
  3. Heterozygote female (phenotypically normal) = 50% transmitting DISEASE to son, 50% transmitting CARRIER to daughter
  4. AFFECTED father will transmit:
    CARRIER to all daughters
    CANNOT transmit disease/carrier to sons

ex. G6PD, Wiskott-Aldrich, hemophilia A/B

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12
Q

Characteristics of X-linked dominant disorders

A
  1. Rarer than X-linked recessive
  2. 2X Females > Males
  3. RARE to have skipped generations
  4. AFFECTED father: DISEASE to all daughters, CANNOT transmit to sons
  5. AFFECTED mother: 50% DISEASE to sons or daughters

Ex: In a family of 6, all girls have a disease but none of the boys do

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13
Q

Presents with:
- camptodactyly
- thick lips
- deep-set eyes
- prominent cupped ears
- deep creases in palms/soles
- mild to severe mental deficiency
- pelvic/hip dysplasia

A

Trisomy 8

Rare, mosaic
Complete Trisomy 8 usually lethal in utero

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14
Q

Presents with:
- Microdeletion from 15q 11-13 of MATERNAL origin (70%)
- inappropriate burst of laughter
- large mouth with protruding tongue
- blonde hair, decreased iris pigment
- initial hypotonia
- severe mental deficiency
- delayed motor skills
- ataxia and jerky movements
- seizures

A

Angelman

“Happy-puppet”

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15
Q

Describe Rubenstein-Taybi syndrome

16p13: cAMP-regulated enhance-binding protein (CREB)

Majority sporadic

A
  1. Cardiac (25%): PDA, VSD, ASD
  2. Broad thumbs and first toes, joint hyper mobility
  3. Downward slanting palpebral issues, hypoplastic maxilla, narrow palate, prominent/BEAKED nose
  4. Hirsutism, cryptorchidism
  5. Microcephaly
  6. Postnatal growth deficiency
  7. Increased risk of tumors- brain, leukemia

risk of developmental delay and mental retardation

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16
Q

Wilm’s tumor
Aniridia
GU abnormalities
Retardation

11p13 deletion

A
  • prominent lips
  • micrognathia
  • malformed ears
  • may develop gonadoblastoma
  • short stature
  • renal failure
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17
Q

How is achondroplasia inherited?

A

Autosomal dominant

80-90% from new mutations
Increase risk with increase paternal age

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18
Q

Physical characteristics of achondroplasia

A
  1. “trident” hands
  2. depressed nasal bridge
  3. megalocephaly
  4. short limps/stature
  5. caudal narrowing of spinal cord
  6. NORMAL intelligence
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19
Q

In-utero findings for Beckwith-Wiedemann

A

POLYHYDRAMNIOS, prematurity

Ear finding: linear earlobe fissures

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20
Q

Holt-Oram syndrome

Autosomal Dominant
Heart-hand syndrome

A
  1. ASD> VSD, Co-arct
  2. upper limb defects
  3. THUMB: absent, hypoplastic, abnormally shaped
  4. narrow shoulders

no correlation between severity of limb defect and cardiac defect

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21
Q

Direction of lens subluxation in Marfan’s

abnormal fibrillin gene at 15q21.1

AD

A

Usually UPWARDS

severe neonatal form can have lens dislocation

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22
Q

What other diagnoses must be considered when thinking about Noonan’s syndrome?

A

fetal hydantoin exposure
fetal alcohol syndrome
45,X/XY

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23
Q

What is the defect in osteogensis imperfecta?

A

Type I collagen

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24
Q

Describe the types of OI

There is significant overlap between all types especially II and III

A
  1. blue sclera, increased risk of fractures, deafness, Wormian bones in cranial sutures, easy bruisability
  2. WORST OUTCOME (stillborn or die early), dark blue sclera, dfractures, short and broad long bones, IUGR
  3. Blue sclera, fractures present at birth, IUGR, abnormal dentition, deafness
  4. normal to grey sclera, ? abnormal dentition
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25
- Flat facies - myopia - spondyloepiphyseal dysplasia (flat vertebrae with anterior wedging, poorly developed distal tibial epiphyses, flat femoral epiphyses) - mitral valve prolapse - **can be associated with Pierre Robin sequence**
Stickler syndrome Hereditary artho-ophthalmopathy when resulting from mutation of type II collagen | AD
26
Cloverleaf skull "Telephone receiver" femurs Platyspondyly (flat vertebral bodies)
Thanatophoric dysplasia | Cloverleaf specifically in Type II
27
Common characteristics of Treacher Collins | AD
lower eyelid coloboma down-slantig palpebral fissures mandibular hypoplasia dysmorphic ears malar hypoplasia conductive hearing loss vision loss NORMAL intelligence | Dx: hypoplastic zygomatic arch on XR
28
Infant with white forelock and partial albinism Deafness (defect in organ of Corti) Lateral displacement of medial canthi (type I) Synophrys
Waardenburg syndrome
29
What is the differential diagnosis for a cephalocele?
1. Meckel-Gruber 2. Amniotic band syndrome 3. Frontonasal dysplasia 4. Walker-Warburg syndrome
30
Describe TAR (thrombocytopenia-absent radii) syndrome | Autosomal recessive
Absent bilateral radii THUMBS ALWAYS PRESENT Ulnar abnormalities (+/- abnormal humerus) Thrombocytopenia (~40% mortality hemorrhage in early infancy) Cardiac abnormalities ~1/3
31
Fanconi Pancytopenia Syndrome Inreased number of chromosomal breaks | AR
Radial hypoplasia Thumb hypoplasia Pancytopenia Hyperpigmentation Short stature ~35% mortality associated with hematologic abnormalities Increased risk of AML
32
Congenital diaphragmatic hernia Coarse facial features Digital and nail hypoplasia
Fryns syndrome
33
What is the most common inherited cause of inherited mental deficiency?
Fragile X Syndrome
34
How did Fragile X get its name?
Finding of X chromosomes cultures in a low folic acid medium that may break near the tip of the long arm
35
Mutation in Fragile X
Triple repeat mutation has >/= 60 CGG | methylated repeats = severity of expression
36
Physical features of Fragile X
long facies prominent forehead large ears large testes post-puberty mental deficiency autism hyperextensible fingers/joints mild connetive tissue dysplasia
37
Infant presents with: twisted, fractures light pigemented hair progressive cerebral deterioration seizures | Due to abnormality in copper transport = copper deficiency
Menkes syndrome Kinky hair syndrome | X-linked recessive
38
Disorders associated with port-wine stains (nevus flammeus): | 85% unilateral, head and neck
Beckwith-Weidemann Cobb syndrome Klippel-Trenaunay-Weber Sturge-Weber
39
Infant with port wine stain, superficial vascular abnormalities, underlying hypertrophy of bones/soft tissues
Klippel-Treynaunay-Weber
40
Port wine stain with underlying spinal angiomas | cutaneomeningospinalangiomatosis
Cobb syndrome
41
Port wine stain with mental deficiency, seizures, hemiparesis contralateral to facial lesion, ipsilateral "tramline" intracortical calcifications
Sturge-Weber
42
Main features of Cat Eye Syndrome | extra part of Ch 22 in quad or triple at 22q11
Cardiac (33%)- TAPVR, persisten L SVC down slanting palpebral fissures anal atreasia coloboma (hence cat-eye) renal agensis
43
Infant with micromelia, synophyrs, thin down-turning upper lip, long and curly eyelashes, initial hypertonicity, microbrachycephaly, hirutism, low posterior hairline
Cornielia de Lange | Mutation in 1 of 3 cohesin-associated genes ## Footnote NIPBL, SMC1L1, SMC3
44
Describe Mobius sequence | associated w/ limb reduction defects, Poland sequence, Klippel-Feil
6th and 7th nerve palsy expressionless facies micrognathia talipes equinovarus 4 types of abnormal development: 1. destruction of central brain nuclei 2. hypoplasia or absence of central brain nuclei 3. peripheral nerve involvement 4. myopathy
45
Pierre Robin sequence
Secondary to mandibular hypoplasia prior to 9 weeks gestation can be associated with Trisomy 18, Stickler syndrome, Treacher-Collins syndrome, fetal alcohol syndrome micrognathia glossoptosis clef palate- U shaped may require intubation for posterior airway obstruction conductive hearing loss tongue-lip adhesion/tracheotomy, mandibular distraction osteogenesis
46
Goldenhar syndrome facio-auriculo-vertebral spectrum | oculo-auriculo-vertebral spectrum
Due to 1st and 2nd brachial arch abnormalities VSD>PDA>TOF>Coarc mouth abnormalities, ear pits/tags tongue abnormalities deafness hemivertebra or hypoplasia of vertebrae (cervical MC) 70% unilateral (right>left) --> hemifacial microsomia renal abnormalities
47
Characteristics of Klippel-Feil sequence
short neck low posterior hairline limited movement of head abnormal cervical vertebrae may have VSD, neurologic deficits, mental deficiency
48
Sequence associated with unilateral hypoplasia or absence of pectoralis muscle | ipsilateral UE abnormalites such as syndactyly
Poland sequence possibly due to proximal subclavian arterial disruption in utero Male>female, 75% right side
49
VACTERL
Diagnosis of exclusion, requires 3 of major abnormalities Vertebral anomalies- 60-90%, scoliosis, tethererd spinal cord Anorectal malformation- 55-90%, imperforate anus, anal atresia, fistula (GU abnormalites as well) Cardiac- 40-80%, VSD>TOF, coarc, vascular anomalies TE fistula- 50-80%, w or w/out esophageal atresia Renal anomaly- 50-80%, renal agensis, cystic/dysplastic kidneys, horseshoe kidney, UPJ obstruction Limb anomalies- 40-55%, upper>lower, raidal>ulnar
50
malformations of bones as a result of an insult during organogensis
dysostoses
51
result from abnormal organization of cells during early patterning events of skeletal development
skeletal dysplasia
52
results from mutated genes that are expressed in chondro-osseus tissue
primary skeletal dysplasia
53
results from abnormalities of extraosseus factors with secondary effects on the skeletal system
secondary skeletal dysplasia
54
What is PCR? How is the test performed?
polymerase chain reaction amplifies a specific DNA sequenc from the genomic DNA by using two primers on either side of the sequence of interest
55
What is arthrogryposis?
Joint contractions due to deformation
56
Where does cell-free DNA come from?
continuous turnover of villous trophoblast results in shedding of apoptotic material including cell-free DNA into the maternal circulation
57
Risk of another anomaly when talipes equinovarus
if diagnosed prenatally, 60% if diagnosed antenatally, 10%
58
Expected finding on Tzank smear for incontinentia pigmenti
Eosinophils
59
Tzank smear shows multinucleated giant cells Diagnosis
Herpes or varicella
60
Tzank smear shows neutrophils Diagnosis?
Neonatal pustular melanosis
61
Infant with anosmia, low FSH and LH
Kallman syndrome | Low FSH/LH due to low HPA activity
62
Infant with optic nerve hypoplasia and absence of the septum pellucidum
Septo-optic dysplasia
63
Fetal condition most likley to pre-dispose to fetal heart rate abnormalities during labor
Potter syndrome
64
What nerve palsy often accompanies choanal atresia?
7th nerve palsy (cant close eye, cant open that side of the mouth) choanal atresia also associated with lop ear anomalie
65
Genetic condition associated with congenital diaphragmatic hernia
Fryn's syndrome Rare, AR digital and nail hypoplasia, coarse facies, cloudy cornea, anteverted nares
66
Most common mitochondrial disorder
Leigh Syndrome *lactate elevated in CSF/blood*
67
Most common genetic condition associated with congenital heart defects
1. Down Syndrome 2. Noonan syndrome (pulm stenosis > cardiomyopathy)
68
Classic triad in Kartagener syndrome
situs inversus bronchiectasis chronic sinusitis
69
Pentalogy of Cantrell
1. Omphalocele 2. Defect of the lower sternum 3. Defect in the pericardium 4. Defect in the anterior diaphragm (diaphragmatic hernia associated with anterior foramen of Morgagni) 5. Cardiac defect (coarctation)
70
Four clinical syndromes associated with hemizygous deletion of chr 22q11
1. DiGeorge 2. Velocardiofacial 3. CHARGE 4. CATCH 22 Diagnosis from FISH Risk for recurrence from affected individual is 50% because AD inheritance pattern
71
Most common causes for severe mental retardation in the US:
1. Downs syndrome 2. FAS (MC preventable cause) 3. Fragile X (MC inherited cause) | iodine deficiency- MC WORLDWIDE cause of preventable mental retardation
72
Most common modification in gene structure is:
Nucleotide variation- changes in single base pairs Known as single nucleotide polymorphisms (SNPs)
73
Infant with broad thumbs and great toes, midface hypoplasia, and variable degrees of craniosynostosis (MC bicoronal)
Pfeiffer syndrome
74
Association of TAR and what allergy?
Cows milk protein
75
Eye finding in Alagille
posterior embryotoxin
76
Malformation
Morphological defect in an organ from an intrinsically abnormal developmental process Something went wrong from the beginning Due to genetic defect or teratogen Can have a high recurrence risk
77
Deformation
Due to compression or distortion of an already normally formed body part Recurrence risk is relatively low
78
Disruption
Breakdown or disruption of the originally normal developmental process, can look like a malformation Recurrence risk is relatively low
79
Major anomaly
Congenital anomaly severe enough to need surgical intervention increased morbidity and/or mortality Potentially has a long term impact medically and/or psychologically
80
Minor anomaly
Congenital anomaly that requires no treatment at all or can be easily corrected Do not cause increase morbidity or mortality Often common in population
81
Noonan: mutation cardiac
PTPN11 PS
82
Alagille
eye: posterior embryotoxon heart: PPS mutation: JAG-1
83
Russell-Silver
84
AD
85
AR
86
XD
87
XR
88
triad of exocrine pancreatic insufficiency, skeletal abnormalities, bone marrow dysfunction (anemia, thrombocytopenia, leukopenia--> recurrent viral/bacterial infections)
Schwachman-Diamond

Neonatology Boards (19 decks)

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