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Neo Boards GF > Genetics > Flashcards

Genetics Flashcards

1
Q

What is the difference between primary mRNA and mature mRNA?

A

Primary has both introns and exons, mature has the introns spliced out. (Both have poly a tail)

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2
Q

What is a southern analysis (or blot/transfer)?

A

DNA digested, placed in gel, then exposed to dna probe to identify the specific fragment.
Used for: detection of point mutations/deletions, triple repeat disorders, methylation differences

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3
Q

What is a northern analysis (or blot/transfer)?

A

RNA is digested, placed in gel. Then a labeled DNA probe is used to identify specific fragment.

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4
Q

What is western analysis?

A

Proteins are placed in gel and antibody is used to identify protein of interest

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5
Q

What is dot blot/reverse dot blot?

A

Dot blot: amplify DNA, apply to membrane, then apply probe that detects mutation. If it matches, hybridization occurs.
Reverse dot blot: put the allele specific oligonucleotides on membrane then add denatured DNA.
Used for: diseases that have specific known mutation, can tell homozygote vs heterozygote

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6
Q

What is crossover frequency?

A

How often recombination of alleles occurs if homologous chromosomes remain attached during prophase. Closer two genes are -> less frequent they will crossover. (Happens with genes further apart)

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7
Q

What is the most common major congenital malformation in US?

A

Neural tube defects

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8
Q

How common are minor malformations?

A

13% of newborns with 1 minor malformation

  1. 8% with 2, 0.5% wth 3
    * If 3 or more, 90% risk of major. If 1, 3% risk of major.
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9
Q

What is a robertsonian translocation?

A

Long arms of 2 diff chromosomes are attached and short arms lost. Offspring will be affected. Causes 3-5% of trisomy 21.

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10
Q

What is inversion?

A

A piece of chromosome is broken and reinserted in opposite direction. Can include centromere (pericentric inversiom) or not include (paracentric inversion)

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11
Q

What is an isochromosome?

A

Breakage at centrome, chromosome has 2 long arms or 2 short arms

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12
Q

What is a ring chromosome?

A

Deletion occurs at both tips -> fuses to form ring -> usually lost, results in monosomy

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13
Q

What is the most common single gene disorder in caucasian population?

A

Cystic fibrosis

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14
Q

What is inheritance pattern of achondroplasia?

A

Autosomal dominant, however almost all are new mutations so usually no family hx or sib recurrence risk

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15
Q

What are diseases causes by trinucleotide repeats?

A

Congential myotonic dystrophy, fragile X, Huntington disease

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16
Q

What is formual for gene frequency/ Hardy Weinberg equilibrium?

A

p + q = 1

p2 + 2pq + q2 = 1

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17
Q

What are findings in trisomy 8?

A 
Camptodactyly (bent finger), thick lips, deep set eyes, cupped ears. 
Usually mosaic (complete trisomy 8 usually lethal in utero)
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18
Q

Trisomy 13

A

Patau syndrome
Midline abnormalities, cutis aplasia, cleft lip/palate, narrow hyperconvex fingernails, holoprosencephaly, persistence of fetal hemoglobin. Cardiac: vsd most common

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19
Q

Trisomy 18

A

Edward syndrome
Females > males (3:1)
VSD, clenched hand, small mouth, short sternum.
Triple screen: low bhcg, low unconjugated estriol, low mat afp

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20
Q

Cri du chat syndrome

A

Partial deletion of chr 5 short arm. Majority de novo. Severe mental deficiency, cat cry, microcephaly, FTT, downward palpebral fissures, hypertelorism, VSD/PDA/TOF

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21
Q

Deletion 13q

A

Thumb hypoplasia, colobomas, retinoblastoma, microcephaly, high nasal bridge.

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22
Q

Angelmann syndrome

A

Deletion of 15q11-13. Deleted piece is always maternal origin.
Sx: inappropriate laughter, blonde hard, protruding tongue, puppet like gait, severe mental deficiency

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23
Q

Prader willi syndrome

A

Deletion 15q11-13 (70% deletion, 25% maternal uniparental disomy). Missing piece is paternal.
Sx: small hands/feet, almond eyes, undescended testes, hypotonia, breech at delivery, FTT -> obesity

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24
Q

DiGeorge syndrome

A

22q11.2 deletion (majority de novo)
Sx: velocardiofacial syndrome, aortic arch anomalies, low Ca, hypoplastic thymus
Defect in 4th brachial arch and 3rd/4th pharyngeal pouches. *most common deletion in humans (1/4000 births)

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25
Q

Rubenstein Taybi syndrome

A

Deletion chr 16p13.3; majority sporadic
Sx: cardiac (25%, pda, vsd, asd); broad thumbs, broad toes. Downward palpebral fissures, hypoplastic maxilla, heavy eyebrows. Inc risk of tumors.

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26
Q

WAGR syndrome

A 
Deletion 11p13; usually de novo
Wilms tumor (50%), Aniridia, GU anomalies, Retardation 
Prominent lips, small jaw, cataracts, short
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27
Q

Williams syndrome

A

Deletion 7q11.23; sporadic
Cardiac: 50-70%; supravalvular subaortic stenosis > PPS (less common vsd, asd, coarct)
Hypoplastic nails, big lips, hoarse voice, blue stellate iris eyes, mental deficiency. High Ca

28
Q

Apert syndrome

A 
Autosomal dominant (usually sporadic), inc risk with old dad, FGFR2 
Sx: wide eyes, midface hypoplasia, broad thumb and toe, syndactyly, coronal craniosynostosis. VSD, PS, overriding aorta
29
Q

Crouzon syndrome

A 
Autosomal dom (variable expression)
FGFR2 gene (diff mut than apert)
Sx: wide eyes, maxillary hypoplasia, shallow orbits, premature craniosynostosis. Less mental def than apert.
30
Q

Beckwith Weidmann syndrome

A

Autosomal dominant, 11p15.5; sporadic
Sx: polyhydramnios and prematurity, large tongue, linear earlobe fissures, exophthalmos. Big head, organ hyperplasia. Fetal adrenocortical cytomegaly. Inc risk of intraabdominal malignancies. Hypoglycemia during infancy.

31
Q

Holt Oram syndrome

A 
Autosomal dominant (variable expression), chr 12
Sx: ASD (most common, also VSD/coarct) 50% w heart defect; missing or small thumbs, narrow shoulders, arm defects.
32
Q

Marfan syndrome

A

Autosomal dominant, fibrillin gene 15q21.1
Sx: dilated aorta, arachnodactyly (long fingers), very flexible, scoliosis, long arms/legs. Lens subluxation (usually upward).
Also a severe neonatal form with heart defects (mitral valve), contractures, high palate, small jaw, long fingers. Different mutation in same gene

33
Q

What treatment is recommended for Marfan syndrome?

A

Beta blocker, decreases rate of aortic dilation

34
Q

Noonan syndrome

A

Autosomal dominant, chr 12
Sx: cardiac (>50%), dysplastic pulmonary valve (less common ASD, cardiomyopathy)
Webbed neck, low hairline, low ears and nasal bridge, downslanting palpebral fissures. Cryptorchidism, abnl coags

35
Q

Osteogenesis imperfecta

A

Type I-III all blue eyes, II most severe. 2 and 3 with fractures at birth. Type IV normal eyes, may have abnormal teeth.

36
Q

Stickler syndrome

A

Autosomal dominant, chr 12. Flat facies, large ears, epicanthialnfolds, small jaw. Eye sx (cataracts, retinal detachment, myopia), deafness. Spondyloepiphyseal dysplasia (flat vertebrae, flat femoral epiphyses)

37
Q

Thanatophoric dysplasia

A

Autosomal dominant, always de novo; mutation of FGFR3 gene tyrosine kinase domain
Cloverleaf skull, short limbs, big head, flat nasal bridge. Severe dev delay. Flat vertebrae. Small thorax. Usually polyhydramnios and die after birth

38
Q

Treacher Collins syndrome

A

Autosomal dominant
Sx: lower eyelid coloboma, down slanting palpebral fissures, small jaw, abnormal ears, malar hypoplasia, no lower eyelashes. Conductive hearing loss (40%), visual loss (40%), normal IQ.
Dx: xray shows hypoplastic zygomatic arch

39
Q

Waardenburg syndrome

A

Usually autosomal dominant. Deafness, pigment abnormalities (white forelock, partial albinism), lateral displacement of medial canthi.
Type IV: also had hirschsprung disease

40
Q

Carpenter syndrome

A

Autosomal recessive
Cardiac (50%): PDA, VSD, asd, PS, TOF, TGA. Polydactyly, lateral placement of inner canthus, shallow orbital ridge, flat nose, corneal opacity. Brachycephaly. FTT, omphalocele. Small genitals

41
Q

Ellis van Creveld syndrome

A

Autosomal recessive
Cardiac (50%): single atrium and ASD, short distal extremities, polydactyly, nail hypoplasia, small thorax. Normal IQ. 50% neonatal mortality

42
Q

Fanconi pancytopenia syndrome

A

AR, inc chr breaks in lymphocytes and amniotic fluid cells. Hyperpigmentation, radial hypoplasia, thumb hypoplasia, short starure. Pancytopenia. Inc risk of AML. Small genitals. 35% mortality due to heme issues

43
Q

Meckel Gruber syndrome

A

AR, cardiac: ASD, VSD, PDA, coarct, PS

Polydactyly, occipital encephalocele, dysplastic kidneys. Small genitals. Small eyes, jaw. Cleft. Abnl ears.

44
Q

Smith Lemli Opitz

A

AR, defect in cholesterol synthesis
Sx: 2nd and 3rd toe syndactyly (95%!), anteverted nostrils, genital abnormalities (70%) hypogenitalis and hypospadias. Small head, low IQ, hypotonic infants. Usually breech. Renal anomalies.
Prenatal dx: low amniotic cholesterol, high 7-dehydrocholesterol

45
Q

TAR (thrombocytopenia-radial aplasia)

A

AR, cardiac (30%): TOF, ASD
No radii, abnormal ulnar borns. Always have thumbs.
Thrombocytopenia (40% die in infancy due to hemorrhage)

46
Q

Fryns syndrome

A

AR; CDH, hirschsprung, duodenal atresia, imperforate anus. Also with dandy walker, hydrocephalus, cloudy cornea, small eyes, cleft lip. Course facial features.

47
Q

What is most common inherited cause of mental deficiency?

A

Fragile X syndrome

48
Q

Fragile X syndrome symptoms

A

Large testes, long face, prominent forehead, large ears. Mental deficiency. Autism. Flexible joints

49
Q

Menkes syndrome

A

X linked recessive; copper deficiency 2/3 abnormal copper transport
Kinky hair syndrome (normal at birth, abnormal by 6 weeks)
Twisted light colored hair, progressive cerebral deterioration, seizures. Inc risk of fractured. Die in early infancy

50
Q

How many turner syndrome are mosaic?

A

30-40%; 50% are true 45 X. Remaining 10-20% are deletion of X

51
Q

What are sx of Turner syndrome?

A

Majority of fetuses w spont abortion. 35% with cardiac (coarct, bicuspid aortic valve, aortic stenosis). Cubitis valgus (forearm away when by side). Cystic hygroma, puffy feet, webbed neck, wide spaced nipples. Inc risk of gonadoblastoma

52
Q

What is treatment for Turner?

A

Growth hormone and estrogen

53
Q

Cat eye syndrome

A

Extra part of 22 (opposite of DiGeorge).

Cardiac (TAPVR, persistent left SVC), anal atresia, down slanting palpebral fissures, coloboma of iris. Renal agenesis

54
Q

Mobius sequence

A

Sporadic, 6th and 7th nerve palsy

Expressionless face, small jaw. Talipes equinovarus (clubfoot)

55
Q

CHARGE association

A 
Happens 35-45 days gestation, autosomal dominant. 
Coloboma
Heart disease (TOF, DORV, VSD, ASD)
Atresia of choanae
Retarded growth/renal anomalies
Genital hypoasia
Ear anomalies
Also w mental deficiency, rib anomalies, TEF
56
Q

Cornelian de Lange syndrome

A

Unknown etiology, mostly sporadic.
Cardiac: VSD > TOF
Small hands/feet (micromelia), 5th finger clinodactyly, syndactyly 2/3rd toes. Unibrow (synophrys), thin down turning uplet lip, long eyelashes. Low hairline, hirsutism

57
Q

Goldenhar syndrome

A

70% unilateral (right>left)
Problem w 1st and 2nd brachial arch
VSD > PDA > TOF > coarct
Malformed ears, ear tags, hypoplasia of face, deafness. Hemivertebrae or hypoplasia of vertebrae

58
Q

Klippel Feil sequence

A

Unknown etiogy, defect in cervical vertebrae.
VSD, short neck, low hairline, limited movement of head. Abnl cervical vertebrae (usually fused). Can have Sprengel deformity (scapula abnl)

59
Q

Klippel Trenaunay Weber

A

Unknown etiology, sporadic

Asymmetric limb hypertrophy, vascular lesions

60
Q

Poland sequence

A

Proximal subclavian arterial disruption in utero. Abnormal arm. With dextrocardia if left sided. Syndactyly of hand, hypoplasia of pectoralus. Renal anomalied. Rib anomalies

61
Q

Russel Silver syndrome

A

Sporadic, some w maternal uniparently disomy

Small triangular facies, small jaw. Short, asymmetric skeleton. Small curved 5th finger. Sweaty with large fontanelles

62
Q

VACTERL association

A 
Sporadic, unknown etiology, increased in diabetic mothers.
Requires 3 of following (many who qualify, half, will have another anomaly)
Vertebral anomalies (70%)
Anal atresia (80%)
Cardiac (50%, VSD > TOF, coarct)
TEF (70%)
Renal anomaly
* majority with normal IQ *
Limb dysplasia
63
Q

What type of neck mass would be behind ear?

A

Branchial cleft cyst (I)

64
Q

What type of neck mass would be just in front of ear?

A

Hemangioma, venous malformation

65
Q

What disorders have port wine stains?

A

Sturge Weber
Klippel Trenauny Weber
Cobb syndrome
Beckwith Wiedeman

66
Q

What percent of trisomy 21 is moasaic?

A

1-2%

67
Q

What percent of translocations causing trisomy 21 are sporadic?

A

75% de novo, 25% familial

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