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49 Cards in this Set

  • Front
  • Back
What is the most common chromosomal disorder and cause of congenital mental retardation?
Down Syndrome (trisomy 21), 1:700
In Down syndrome, 4% of cases are due to ------- translocation, and 1% are due to -------- mosaicism
Robertsonian; Down
95% of Down syndrome cases occur because of --------- --------- of homologous chromosomes
meiotic nondisjunction
What is the type and cause of the most common congenital heart malformation in Down syndrome?
Septum-primum-type ASD due to endocardial cushion defects
Name 8 findings in trisomy 21
(1) mental retardation (2) flat facial profile (3) prominent epicanthal folds (4) simian crease (5) duodenal atresia (6) congenital heart disease (7) Alzheimer's in affected >35 yrs old (8) Increased risk of ALL
Name a risk factor for Down Syndrome
Advanced maternal age (1:500 < 20 yo; 1:25 > 45 yo)
What is the name of the syndrome associated with trisomy 18?
Edwards' syndrome (Election age = 18)
Name 7 findings in trisomy 18
(1) severe mental retardation (2) rocker bottom feet (3) low-set ears (4) microngathia (5) congenital heart dz (6) clenched hands (flexion of fingers) (7) prominent occiput
What is the life expectancy in trisomy 18?
Death usually w/in 1 year of birth
What chromosomal anomaly is found in Patau's syndrome?
trisomy 13 (1:6000)
Name 7 findings in Patau's
(1) severe mental retardation (2) microphthamlia (3) microcephaly (4) cleft lip/palate (5) abnormal forebrain structures (6) polydactyly (7) congenital heart dz
What is the life expectancy in Patau's?
Death usually w/in 1 year of birth
What is the chromosomal anomaly in Klinefelter's syndrome?
XXY (1:850) - male
Name 5 characteristics of Klinefelter's syndrome
(1) Testicular atrophy (2) Enuchoid body shape (3) Tall, long extremities (4) Gynecomastia (5) Female hair distribution
What is a Barr body and is it found kin Klinefelter's syndrome?
It is the inactivated X chromosome. Yes.
What is the chromosomal anomaly in Turner's syndrome?
Female XO; (1:3000)
Name 4 characteristics of Turner's syndrome
(1) Short stature (2) Ovarian dysgenesis (streak ovary) (3) Webbing of next (4) Coarctation of the aorta
Turner's syndrome is the most common cause of primary ------------
Is there a Barr body in Turner's syndrome?
Double Y males have what genotype?
XYY (1:1000) - male
What is the double Y phenotype?
Normal phenotype, very tall, severe acne, antisocial behavior (seein in 1-2% of XYY males; seen increasingly among prison inmates)
How are muscular dystrophies diagnosed?
Elevated CPK and muscle biopsy
What is the gene involved in muscular dystrophy?
What is the mutation in Duchenne's MD?
Frame-shift mutation - deletion of dystrophin gene - accelerated muscle breakdown.
What is the age of onset in Duchenne's MD?
Before 5 years
In what muscles does weakness begin with Duchenne's MD?
Pelvic girdle muscles and progresses superiorly
Name 3 diagnostic characteristics of Duchenne MD.
(1) Pseduohypertrophy of calf muscles due to fibrofatty replacement of muscle (2) Cardiac myopathy (3) Use of Gowers' maneuver, requiring assistance of upper extremities to stand up - indicates proximal lower limb weakness
What distinguishes Becker's from Duchenne's MD?
Less severe mutation in Becker's. Less debilitating.
What is pseudohermaphroditism?
Disagreement between the phenotypic (external genitalia) and gonadal (testes vs. ovaries) sex.
A female pseudohermaphrodite has ------- present, but external genitalia are -------- or -----------.
ovaries; virilized or ambiguous
What causes female pseudohermaphroditism?
Excessive and inappropraite exposure to androgenic steroids during early gestation (i.e.,congenital adrenal hyperplasia or exogenous administration of androgens suring pregnancy).
What are the phenotypes in female and male pseudohermaphroditism?
female - XX; male - XY
A male pseudohermaphrodite has ------- present, but external genitalia are --------- or ---------.
testes; female or ambiguous
What is the most common form of male pseudohermaphroditism?
Testicular feminization (androgen insensitivity), which results from a mutation in the androgen receptor gene (x-linked); blind-end vagina
What determines gender identity?
External genitalia and sex of upbringing.
What is a true hermaphrodite?
Both ovary and testicular tissue present; ambiguous genitalia.
What are the genotypic possibilities for a true hermaphrodite?
46,XX or 47,XXY
What is the molecular defect in testicular feminization syndrome?
Defect in DHT receptor resulting in normal-appearing female
What genitalia are present in testicular feminization syndrome?
female genitalia with rudimentary vagina; uterus and uterine tubes generally absent; develop testes (often found in labia majora; surgically removed to prevent malignancy)
What are the genotype and horomone levels in testicular feminization syndrome?
46, XY; levels of testosterone, estrogen and LH are all high
What is the biochemical consequence of 5a-reductase deficiency
Unable to convert testosterone to DHT.
Describe genital development in 5a-reductase deficiency.
Ambiguous genitalia until puberty, when increased testosterone causes masculinization of genitalia.
What are the hormone levels in 5a-reductase deficiency.
Testosterone/estrogen levels are normal; LH is normal or elevated.
What is the mutation in Cri-du-chat syndrome?
Congenital deletion of short arm of chromosome 5 (46,XX or XY, 5p-)
What are the findings in Cri-du-chat
Microcephaly, severe mental retardation, high-pitched crying/mewing, epicanthal folds, cardiac abnormalities.
What does Cri-du-chat mean in english, which might help remember the symptoms?
Cry of the cat.
What is the 2nd most common cause of genetic mental retardation?
Fragile X syndrome
What genetic change is involved in Fragile X syndrome?
x-linked defect affecting the methylation and expression of the FMR1 gene.
Name 4 physical features associated with Fragile X syndrome?
(1) macro-orchidism (enlarged testes) (2) Long face with a large jaw (3) large everted ears (4) autism