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