Lecture 9: Cytogenetics I Flashcards
What is the karyotype for Trisomy 13?
47,XX,+13 (female)
47,XY,+13 (male)
What is the eponym for Trisomy 13?
Patau
What are the clinical features of Trisomy 13?
- Midline deformations
- Microcephaly
- CHD
- Scalp defects (cutis aplasia)
- Holoprosencephaly
- Microphtalmia
- Cleft palate
- Polydactyly
- Renal anomalies
List all three trisomies in order of their incidence rates.
Trisomy 13: 1-2 in 10,000 (low)
Trisomy 18: 1-2 in 6,000 (medium)
Trisomy 21: 1 in 700 (high)
What is the prognosis for Trisomy 13?
Poor, 95% die in the first six months.
What is the karyotype for Trisomy 18?
47,XX,+18 (female)
47,XY,+18 (male)
What is the alternative name for Trisomy 18?
Edwards
What are the clinical features of Trisomy 18?
- Small size
- Small head circumference
- Congenital heart defects
- Overlapping fingers
- Rocker bottom feet
What is the prognosis for Trisomy 18?
Poor, 95% die within 12 months.
What is the karyotype for Trisomy 21?
47,XX,+21 (female)
47,XY,+21 (male)
What is the alternative name for Trisomy 21?
Down
What are the clinical features of Trisomy 21?
- Flat facial profile
- Upslanted palpebral fissures
- Anomalous auricles
- Nuchal skin fold
- Single palmar crease
- Clinodactyly
- Hypotonia
- Hyperflexible joints
- Intellectual Disability
- Sandle gap
What is the prognosis for Trisomy 21?
Live into 50s/60s.
What is the karyotype of Turner Syndrome?
45,X
What are the clinical features of Turner Syndrome?
- Lymphedema in infancy
- Bicuspid aortic valve
- Coarctation of aorta
- Short stature
- Gonadal regression (streak ovaries)
- Low posterior hairline
- Webbed neck
- Widely spaced nipples
- Horseshoe kidney
- Cubitus valgus of elbow
What is the prognosis for Turner Syndrome?
Good, however the vast majority are lost as SABs. Only few live.
What is the karyotype for Klinefelter Syndrome?
47,XXY
What are the clinical features of Klinefelter Syndrome?
- Tall stature
- Long limbs
- Learning disabilities
- Gynecomastia (post-puberty)
- Small testicles
- Infertility
What are the clinical features of 47,XXY males?
- Normal physical appearance
- Stature is above average
- Intelligence is usually normal
- IQ scores are often 10-15 points below that of siblings
- Emotional immaturity and impulsive behavior
What are the clinical features of 47,XXX females?
- Physical appearance is usually normal
- IQ is generally 10-15 points below that of siblings
- Verbal language is often delayed
- Women with 47,XXX karyotypes usually have normal fertility but there is an increased incidence of fertility problems compared to the normal population.
Monosomy
Occurs from non-disjunction; the cell is shorted one chromosome.
Trisomy
Occurs from non-disjunction; the cell gains a chromosome.
When does heterodisomy (UPD) occur?
M1 block
When does isodisomy (UPD) occur?
M2 block
