Genetics Abnormal Amnio Chromosome Abnormalities

Front 1

What is the difference between a malformation, a deformation and a developmental field defect

Back 1

Deformation: A change from the normal size or shape of an anatomic structure due to mechanical forces that distort an otherwise normal structure. occur most often late in pregnancy or during delivery. A twin pregnancy can cause deformations due to crowding of the twins late in pregnancy. ex)molding of the head of a baby born by vaginal delivery. There are usually no significant lasting effects.

A deformation is different from a malformation in timing and impact. In a malformation, the development of a structure is arrested, delayed, or misdirected early in embryonic life and the effect is permanent.

field defect is when there is disturbed development of a related group of cells in the embryo ex) bowel and bladder anomalies associated with sacral agenesis

Front 2

fertilization of haploid egg by two sperm

Back 2

dispermy

Front 3

fertilization of diploid egg due to maternal non-disjunction

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digyny

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fertilization of egg by a diploid sperm

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diandry

Front 5

what are causes of triploidy?

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mosaicism, diandry digyny dispermy

Front 6

One or a few chromosomes above or below the normal chromosome number.

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aneuploidy

Front 7

trisomy 21
frequency
clinical features
Complications

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frequency - 1/1000, 2% are mosaics, 3-4% are translocations

clinical features - hypotonia (low muscle tone), single palmar crease, congenital heart disease, extra nuchal folds, small, delayed development

Complications: hypothyroidism, seizures, leukemia, shortned lifespan, hyperbilirubinemia in neonatal period

Front 8

Trisomy 18 (edwards syndrome)
Frequency
Clinical features

Back 8

Frequency: 1/6600, aneuploid instances are age-related

Clinical features - growth retardation, congenital malformations (cleft lip, heart, esophogeal atresia, renal malformations) hypotonia at first, hypertonia and mental retardation in survivors,
80% don't survive first year

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Trisomy 13 Patau Syndrome
frequency
Clinical features

Back 9

Frequency: 1/8000
anueploid patients assoc with older age

Clinical: microcephaly, holoprosencephly, microphthalmia (small eyes), mental retardation, 95% deceased by age 3

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NOTE rates of trisomies are greater at conception than they are at birth b/c a lot of them die before they are birthed, so a woman has a higher risk of conceiving a trisomy baby than she has of actually having a trisomy baby

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kjg

Front 11

Turner Syndrome 45 x

Back 11

Frequency: 1/5000
not related to maternal age

Clinical features:
ovarian dysgenesis(lack of development, ammenhorea, sterility), extra nuchal folds, short webbed neck, widley spaced nipples, coarctation of the aorta( horshoe kidneys)

Complications: diabetes, hypertension specific learning disabilities, short

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Kleinfelters XXY

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1/1000

Small testicles, sterility, tall, gynecomastia, specific learning disabilities, behavior/emotional problems

Front 13

XYY male

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1/1000

tendency for tall stature, educational difficulties, radial ulnar syntosis

Front 14

what is the most common cause of trisomies?

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maternal meiotic nondisjunction, mostly in mei 1

Front 15

what diseases have risk increase with maternal age

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downs
trisomy 13 in aneuploid patients (not mosaics and translocation
trisomy 18 in aneuploid

Front 16

in turner syndrome is matenal or paternal non disjunction more commonly the cause?

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paternal nondisjunction in most frequently the cause

Front 17

are most trisomic infants born to over or under 35

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under 35, because most women have children under this age

Front 18

Cri-Du-Chat 5p-
freq
mechanism
clinical

Back 18

freq: 1/20,000
mech: de novo or translocation
clinical: microcephaly, weak cry

Front 19

how do you detect a microdeletion?

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high resolution banding
if still too small, use FISH, can't just send blood for analysis, must specify which FISH probe according to the syndrome you want to use

Front 20

paternal chromosome 15 has a deletion

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cause of prader willi

Front 21

maternal chromosome 15 has a deletion

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cause of angelmans

Front 22

the disturbance of two or more unrelated henes in a chromosomal region to produce a consistent and recognizable phenotype

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contiguous gene syndromes ie prader willi

Front 23

general indications for chromosomal analysis

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SGA, microencephaly, mental retardation, malformations, hypotonia, or those with symptoms who dont fit a standard single gene syndrome, still birth or neonatal death

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who should get chromosomal analysis

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parents of a dysmorphic chille out balanced, 3 or more reproductive losses, persons of any age with reproductive difficulties

Front 25

anytime you see monosomy or partial trisomy what should you do

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study the parents to rule out balanced translocation