genetic diseases pathology
Terms
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- 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 ------------
- amenorrhea
- Is there a Barr body in Turner's syndrome?
- No
- 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?
- Dystrophin
- 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