Chromosomal Disorders

Question 1

what is the most common chromosome abnormality in live-born babies

Answer 1

trisomy 21

Question 2

what is the most common cause of intellectual disability in the population

Answer 2

trisomy 21

Question 3

common features of trisomy 21

Answer 3

upslanting palpebral fissures, single transverse palmar creases, generalized hypotonia, microcephaly, short stature

Question 4

other defects in trisomy 21

Answer 4

AV canal, duodenal atresia, increased risk of megakaryoblastic leukemia (and other leukemias), hypothyroidism, increased incidence of Alzheimers (related to APP gene)

Question 5

mosaicism

Answer 5

the presence of 2 or more populations of cells with different genotypes in one individual who has developed from a single fertilized egg

Question 6

trisomy 13 (patau syndrome)

Answer 6

low life expectancy; cutis aplasia (scalp defect), microphthalmia, postaxial polydactyly, holoprosencephaly, severe intellectual disability

Question 7

trisomy 18 (edwards syndrome)

Answer 7

clinical features: prenatal and postnatal growth deficiencies, overlapping fingers, rocker bottom feet

Question 8

Turner syndrome (45, X)

Answer 8

single copy of X chromosome; exclusive to FEMALES; at increased risk for X-linked recessive disorders; aortic coarctation, DOWN-slanting palpebral fissures, horseshoe kidney, webbed neck, lack of pubertal development; infertile

Question 9

Klinefelter syndrome (47, XXY)

Answer 9

extra X chromosome in MALES; leading cause of male infertility; tall stature, reduced secondary sex characteristics, gynecomastia

Question 10

22q11.2 deletion syndrome

Answer 10

CATCH 22:
Cardiac abnormality
Abnormal facies
Thymic hypoplasia/aplasia
Cleft palate
HYPOcalcemia
*Tetralogy of Fallot
*increased risk of schizophrenia
*immune deficiency

Question 11

Williams syndrome

Answer 11

deletion on 7q11.23; stellate irides, periorbital fullness, wide mouth, widely spaced teeth, large ear lobes; COCKTAIL PARTY PERSONALITY, supravalvular aortic stenosis, HYPERcalcemia

Question 12

cri-du-chat syndrome

Answer 12

5p minus; differences in structure of larynx associated with UNUSUAL, HIGH-PITCHED CRY; hypertelorism, microcephaly, downturned mouth, behavioral issues (aggressiveness, etc)

Question 13

Prader-Willi syndrome

Answer 13

ABNORMAL FOOD-SEEKING BEHAVIORS or insatiable appetite; almond shaped eyes, obesity

Question 14

Angelman syndrome

Answer 14

“Happy Puppet = always laughing and smiling, ATAXIA, seizures, no speech

Question 15

genetics of Prader-Willi syndrome

Answer 15

Paternal deletion (on 15q11-q13)

Question 16

genetics of angelMan syndrome

Answer 16

Maternal deletion (on 15q11-q13)