5 main features of T21
Hypotonia, ID, flat facial profile, CHD, GI anomalies
Most common genetic cause of T21
Nondisjunction
Mosacism is always a _____ event
Mitotic
RR for nondisjunction T21
1% OR maternal age risk
5 major features of T18
Hypertonia, clenched fist with overlapping 3rd and 4th finger, rocker-bottom feet, ID, hernia
RR for T18
Less than 1% (since most SAB)
5 major features of T13
(Midline) HPE, CL+P, polydactyly, omphalocele, ID+ seizures
RR for T13
Less than 1% (since most SAB)
5 major features of 22q11
Velopharngyeal incompetence, CHD, asymmetric crying facies, immunodeficiency, hypocalcemia
Is 22q usually de novo or inherited
de novo
5 major features of XXY
Hypogonadism, infertility, lower IQ than sibs, behaviour problems, gynecomastia
Treatment for XXY
Testosterone supplementation
5 major features of XO
Short stature, gonadal dysgenesis, webbed neck, CHD, transiet congenital lymphedema
Treatment for XO
Estrogen replacement therapy
Risk for 45, X/ 46, XY Mosaics
Gonadoblastoma
What is used to stop the cell cycle in metaphase when making a karyotype
Colchicine
Best uses for FISH
Partial/full aneuploidy–but you must known what you are looking for
Array CGH cannot detect
Balanced translocations, triploidy
SNP-array is useful for detecting:
Consanguinity (ROHs), triploidy, UPD
4 posible gametes for reciprocal translocation carrier
Normal, Balanced, Unbalanced (two forms)
3 major features of Cri du Chat
Cat-like cry, microcephaly, low birth weight
Where is deletion in Cri du Chat
5p
3 major features of Wolf Hirschhorn
Greek warrior helmet appearance, FTT, ID
Where is deletion in Wolf Hirschhorn
4p16.3
3 major features of 1p36.3 del
severe ID, seizures, behaviour problems
Where is deletion in 1p36.3
1p36.3
3 major features of William’s Syndrome
Elfin face, outgoing personality, supravalvular aortic stenosis
Where is deletion in William’s Syndrome
7q11.23
T/F: X-inactivation affects all genes
False
2 major features of Miller Dieker Syndrome
Type 1 lishencephaly, dysmorphic facies
Where is deletion in Smith Magenis
17p11.2
3 major features in Smith Magenis
Self-destructive behaviour, peripheral neuropathy, ID
Deletion in Prader Willi
15q11-q13
What parent’s copy is missing in PWS
Dad
What parent’s copy is missing in Angelman
Mom
Where is deletion in Angelman
15q11-q13
3 major features of Prader Willie
Infantile hypotonia, hyperphagia, hypogenitalism
3 major features of Angelman
Seizures, Unusual laughter, ataxic gait
Where is duplication in BWS
11p15
3 major features in BWS
Macrosomia, Macroglossia, Omphalocele
Alternate segregation usually leads to balanced or unbalanced gametes?
Balanced
Adjacent segregation usually leads to balanced or unbalanced gametes?
Unbalanced
Centromeres in Adjacent 1
Unlike centromeres travel together
Centromeres in Adjacent 2
Like centromeres travel together
Tertiary 3:1 Segregation
2 normal chromosomes; 1 translocation chromosome
Interchange 3:1 Segregation
2 translocation chromosomes; 1 normal chromosome
List afrocentric chromosomes
13, 14, 15, 21, 22, Y
RR if mom passes t(13;21)
15%
RR if mom passes t(14;21)
10%
RR if mom passes t(21;22)
10%
Paracentric Inversion
Breaks in either short arm or long arm, no centromeres involved
Pericentric Inversion
Break in the short arm and long arm, centromeres involved
Inversions in what chromosomes are considered normal variation?
1, 9, 16, Y