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Neonatology Boards > Genetics > Flashcards

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
Q
  • 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
A

Stickler syndrome

Hereditary artho-ophthalmopathy when resulting from mutation of type II collagen

AD

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26
Q

Cloverleaf skull
“Telephone receiver” femurs
Platyspondyly (flat vertebral bodies)

A

Thanatophoric dysplasia

Cloverleaf specifically in Type II

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27
Q

Common characteristics of Treacher Collins

AD

A

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

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28
Q

Infant with white forelock and partial albinism
Deafness (defect in organ of Corti)
Lateral displacement of medial canthi (type I)
Synophrys

A

Waardenburg syndrome

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29
Q

What is the differential diagnosis for a cephalocele?

A
  1. Meckel-Gruber
  2. Amniotic band syndrome
  3. Frontonasal dysplasia
  4. Walker-Warburg syndrome
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30
Q

Describe TAR (thrombocytopenia-absent radii) syndrome

Autosomal recessive

A

Absent bilateral radii
THUMBS ALWAYS PRESENT
Ulnar abnormalities (+/- abnormal humerus)
Thrombocytopenia (~40% mortality hemorrhage in early infancy)
Cardiac abnormalities ~1/3

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31
Q

Fanconi Pancytopenia Syndrome

Inreased number of chromosomal breaks

AR

A

Radial hypoplasia
Thumb hypoplasia
Pancytopenia
Hyperpigmentation
Short stature
~35% mortality associated with hematologic abnormalities
Increased risk of AML

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32
Q

Congenital diaphragmatic hernia
Coarse facial features
Digital and nail hypoplasia

A

Fryns syndrome

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33
Q

What is the most common inherited cause of inherited mental deficiency?

A

Fragile X Syndrome

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34
Q

How did Fragile X get its name?

A

Finding of X chromosomes cultures in a low folic acid medium that may break near the tip of the long arm

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35
Q

Mutation in Fragile X

A

Triple repeat mutation
has >/= 60 CGG

methylated repeats = severity of expression

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36
Q

Physical features of Fragile X

A

long facies
prominent forehead
large ears
large testes post-puberty
mental deficiency
autism
hyperextensible fingers/joints
mild connetive tissue dysplasia

37
Q

Infant presents with:
twisted, fractures light pigemented hair
progressive cerebral deterioration
seizures

Due to abnormality in copper transport = copper deficiency

A

Menkes syndrome
Kinky hair syndrome

X-linked recessive

38
Q

Disorders associated with port-wine stains (nevus flammeus):

85% unilateral, head and neck

A

Beckwith-Weidemann
Cobb syndrome
Klippel-Trenaunay-Weber
Sturge-Weber

39
Q

Infant with port wine stain, superficial vascular abnormalities, underlying hypertrophy of bones/soft tissues

A

Klippel-Treynaunay-Weber

40
Q

Port wine stain with underlying spinal angiomas

cutaneomeningospinalangiomatosis

A

Cobb syndrome

41
Q

Port wine stain with mental deficiency, seizures, hemiparesis contralateral to facial lesion, ipsilateral “tramline” intracortical calcifications

A

Sturge-Weber

42
Q

Main features of Cat Eye Syndrome

extra part of Ch 22 in quad or triple at 22q11

A

Cardiac (33%)- TAPVR, persisten L SVC
down slanting palpebral fissures
anal atreasia
coloboma (hence cat-eye)
renal agensis

43
Q

Infant with micromelia, synophyrs, thin down-turning upper lip, long and curly eyelashes, initial hypertonicity, microbrachycephaly, hirutism, low posterior hairline

A

Cornielia de Lange

Mutation in 1 of 3 cohesin-associated genes

NIPBL, SMC1L1, SMC3

44
Q

Describe Mobius sequence

associated w/ limb reduction defects, Poland sequence, Klippel-Feil

A

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
Q

Pierre Robin sequence

A

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
Q

Goldenhar syndrome

facio-auriculo-vertebral spectrum

oculo-auriculo-vertebral spectrum

A

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
Q

Characteristics of Klippel-Feil sequence

A

short neck
low posterior hairline
limited movement of head
abnormal cervical vertebrae

may have VSD, neurologic deficits, mental deficiency

48
Q

Sequence associated with unilateral hypoplasia or absence of pectoralis muscle

ipsilateral UE abnormalites such as syndactyly

A

Poland sequence

possibly due to proximal subclavian arterial disruption in utero
Male>female, 75% right side

49
Q

VACTERL

A

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
Q

malformations of bones as a result of an insult during organogensis

A

dysostoses

51
Q

result from abnormal organization of cells during early patterning events of skeletal development

A

skeletal dysplasia

52
Q

results from mutated genes that are expressed in chondro-osseus tissue

A

primary skeletal dysplasia

53
Q

results from abnormalities of extraosseus factors with secondary effects on the skeletal system

A

secondary skeletal dysplasia

54
Q

What is PCR? How is the test performed?

A

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
Q

What is arthrogryposis?

A

Joint contractions

due to deformation

56
Q

Where does cell-free DNA come from?

A

continuous turnover of villous trophoblast results in shedding of apoptotic material including cell-free DNA into the maternal circulation

57
Q

Risk of another anomaly when talipes equinovarus

A

if diagnosed prenatally, 60%

if diagnosed antenatally, 10%

58
Q

Expected finding on Tzank smear for incontinentia pigmenti

A

Eosinophils

59
Q

Tzank smear shows multinucleated giant cells
Diagnosis

A

Herpes or varicella

60
Q

Tzank smear shows neutrophils
Diagnosis?

A

Neonatal pustular melanosis

61
Q

Infant with anosmia, low FSH and LH

A

Kallman syndrome

Low FSH/LH due to low HPA activity

62
Q

Infant with optic nerve hypoplasia and absence of the septum pellucidum

A

Septo-optic dysplasia

63
Q

Fetal condition most likley to pre-dispose to fetal heart rate abnormalities during labor

A

Potter syndrome

64
Q

What nerve palsy often accompanies choanal atresia?

A

7th nerve palsy (cant close eye, cant open that side of the mouth)

choanal atresia also associated with lop ear anomalie

65
Q

Genetic condition associated with congenital diaphragmatic hernia

A

Fryn’s syndrome

Rare, AR
digital and nail hypoplasia, coarse facies, cloudy cornea, anteverted nares

66
Q

Most common mitochondrial disorder

A

Leigh Syndrome
lactate elevated in CSF/blood

67
Q

Most common genetic condition associated with congenital heart defects

A
  1. Down Syndrome
  2. Noonan syndrome (pulm stenosis > cardiomyopathy)
68
Q

Classic triad in Kartagener syndrome

A

situs inversus
bronchiectasis
chronic sinusitis

69
Q

Pentalogy of Cantrell

A
  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
Q

Four clinical syndromes associated with hemizygous deletion of chr 22q11

A
  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
Q

Most common causes for severe mental retardation in the US:

A
  1. Downs syndrome
  2. FAS (MC preventable cause)
  3. Fragile X (MC inherited cause)

iodine deficiency- MC WORLDWIDE cause of preventable mental retardation

72
Q

Most common modification in gene structure is:

A

Nucleotide variation- changes in single base pairs
Known as single nucleotide polymorphisms (SNPs)

73
Q

Infant with broad thumbs and great toes, midface hypoplasia, and variable degrees of craniosynostosis (MC bicoronal)

A

Pfeiffer syndrome

74
Q

Association of TAR and what allergy?

A

Cows milk protein

75
Q

Eye finding in Alagille

A

posterior embryotoxin

76
Q

Malformation

A

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
Q

Deformation

A

Due to compression or distortion of an already normally formed body part

Recurrence risk is relatively low

78
Q

Disruption

A

Breakdown or disruption of the originally normal developmental process, can look like a malformation

Recurrence risk is relatively low

79
Q

Major anomaly

A

Congenital anomaly severe enough to need surgical intervention
increased morbidity and/or mortality
Potentially has a long term impact medically and/or psychologically

80
Q

Minor anomaly

A

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
Q

Noonan:
mutation
cardiac

A

PTPN11
PS

82
Q

Alagille

A

eye: posterior embryotoxon
heart: PPS
mutation: JAG-1

83
Q

Russell-Silver

A
84
Q

AD

A
85
Q

AR

A
86
Q

XD

A
87
Q

XR

A
88
Q

triad of exocrine pancreatic insufficiency, skeletal abnormalities, bone marrow dysfunction (anemia, thrombocytopenia, leukopenia–> recurrent viral/bacterial infections)

A

Schwachman-Diamond

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