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Genetics Flashcards

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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
Rubenstein Taybi syndrome
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.
26
WAGR syndrome
``` Deletion 11p13; usually de novo Wilms tumor (50%), Aniridia, GU anomalies, Retardation Prominent lips, small jaw, cataracts, short ```
27
Williams syndrome
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
Apert syndrome
``` 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
Crouzon syndrome
``` 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
Beckwith Weidmann syndrome
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
Holt Oram syndrome
``` 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
Marfan syndrome
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
What treatment is recommended for Marfan syndrome?
Beta blocker, decreases rate of aortic dilation
34
Noonan syndrome
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
Osteogenesis imperfecta
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
Stickler syndrome
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
Thanatophoric dysplasia
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
Treacher Collins syndrome
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
Waardenburg syndrome
Usually autosomal dominant. Deafness, pigment abnormalities (white forelock, partial albinism), lateral displacement of medial canthi. Type IV: also had hirschsprung disease
40
Carpenter syndrome
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
Ellis van Creveld syndrome
Autosomal recessive Cardiac (50%): single atrium and ASD, short distal extremities, polydactyly, nail hypoplasia, small thorax. Normal IQ. 50% neonatal mortality
42
Fanconi pancytopenia syndrome
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
Meckel Gruber syndrome
AR, cardiac: ASD, VSD, PDA, coarct, PS | Polydactyly, occipital encephalocele, dysplastic kidneys. Small genitals. Small eyes, jaw. Cleft. Abnl ears.
44
Smith Lemli Opitz
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
TAR (thrombocytopenia-radial aplasia)
AR, cardiac (30%): TOF, ASD No radii, abnormal ulnar borns. Always have thumbs. Thrombocytopenia (40% die in infancy due to hemorrhage)
46
Fryns syndrome
AR; CDH, hirschsprung, duodenal atresia, imperforate anus. Also with dandy walker, hydrocephalus, cloudy cornea, small eyes, cleft lip. Course facial features.
47
What is most common inherited cause of mental deficiency?
Fragile X syndrome
48
Fragile X syndrome symptoms
Large testes, long face, prominent forehead, large ears. Mental deficiency. Autism. Flexible joints
49
Menkes syndrome
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
How many turner syndrome are mosaic?
30-40%; 50% are true 45 X. Remaining 10-20% are deletion of X
51
What are sx of Turner syndrome?
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
What is treatment for Turner?
Growth hormone and estrogen
53
Cat eye syndrome
Extra part of 22 (opposite of DiGeorge). | Cardiac (TAPVR, persistent left SVC), anal atresia, down slanting palpebral fissures, coloboma of iris. Renal agenesis
54
Mobius sequence
Sporadic, 6th and 7th nerve palsy | Expressionless face, small jaw. Talipes equinovarus (clubfoot)
55
CHARGE association
``` 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
Cornelian de Lange syndrome
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
Goldenhar syndrome
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
Klippel Feil sequence
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
Klippel Trenaunay Weber
Unknown etiology, sporadic | Asymmetric limb hypertrophy, vascular lesions
60
Poland sequence
Proximal subclavian arterial disruption in utero. Abnormal arm. With dextrocardia if left sided. Syndactyly of hand, hypoplasia of pectoralus. Renal anomalied. Rib anomalies
61
Russel Silver syndrome
Sporadic, some w maternal uniparently disomy | Small triangular facies, small jaw. Short, asymmetric skeleton. Small curved 5th finger. Sweaty with large fontanelles
62
VACTERL association
``` 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
What type of neck mass would be behind ear?
Branchial cleft cyst (I)
64
What type of neck mass would be just in front of ear?
Hemangioma, venous malformation
65
What disorders have port wine stains?
Sturge Weber Klippel Trenauny Weber Cobb syndrome Beckwith Wiedeman
66
What percent of trisomy 21 is moasaic?
1-2%
67
What percent of translocations causing trisomy 21 are sporadic?
75% de novo, 25% familial

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