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GeneticDisorders-III
lecture 27 wilson
| Question | Answer |
|---|---|
| multifactorial inheritance | determined by 2 or more genes, conditioned by non-genetic influences; examples: cleft lip or palate, congenital heart dz, CAD, HTN, gout, DM, pyloric stenosis |
| advantages of FISH over cytogenetics | able to detect submicroscopic aberrations, can use non-dividing (in interphase) cells for analysis |
| Down syndrome | trisomy 21, most common constitutional chr abnormality, 1/700 births, associated with advanced maternal age |
| physical features of Down syndrom | prominent epicanthal folds, low-set ears, macroglossia, MR, abundant neck skin, duodenal atresia ("double bubble"), congenital heart defects, HYPOtonicity, predisposition to leukemia |
| del(22q11.2) or DiGeorge/velocardiofacial syndrome | microdeletion syndrome causing nasal-sounding speech, congenital heart defects, hypocalcemia and T-cell immunodeficiency b/c 4th pharyngeal pouch is absent = thymic and parathyroid a/hypoplasia |
| trisomy 18 (Edwards syndrome) | lethal trisomy, 1/8000 births, clenched fists/HYPERtonicity can be seen on son, clinodactyly, intrauterine growth defects, congenital heart problems |
| trisomy 13 (Patau syndrome) | lethal trisomy, midline defects = cleft lip and palate, holoprosencephaly, fusion of frontal lobes, agenesis of cerebellar vermis |
| term for inactivation of one X chr | lyonization |
| heteropyknosis of one X chr results in? | Barr body, occurs after 16th day of life |
| higher # of X chr can be associated with greater likelihood of phenotypic effect and MR | XXY, XXXY |
| Turner syndrome | 45XO, 1/2-3,000 births; phenotype: short stature, coarctation of aorta, webbed neck, streak ovaries = menopause before menarche, widely-spaced nipples. usually short females without mental compromise |
| Klinefelter syndrome | XXY or XXXY, 1/500 births, more common than Down syndrome, phenotype: hypogonadism, pear-shaped figure due to overproduction of androgens that are converted peripherally to estrogen, long legs, infertility, no MR |
| genetic sex | determined by presence/absence of sex-determining region of the Y chr (SRY gene) |
| gonadal sex | histological appearance of gonads |
| ductal sex | presence of Mullerian or Wolffian ducts |
| genital or phenotypic sex | appearance of external genitalia |
| true hemaphrodite | have both ovarian and testicular tissue, XX- or XY- cell lines |
| female hemaphrodite | XX with ovaries but male external genitalia b/c they weren't able to respond to estrogens in utero. CAH - defect in enzyme resulting in overproduction of androgens |
| male hemaphrodite | Y chr and testes but external genitalia are ambiguous or overtly female, results from androgen insensitivity, AR is defective so not able to respond even to nl levels of testosterone/DHT |
| Fragile X syndrome | X-linked disorder, 200 or more CGG repeats in noncoding region of FMR-1 gene; phenotype: long face and mandible, large and everted ears, macro-orchidism, 2nd most common cause of MR |
| inheritance pattern of fragile X syndrome | X-linked with differences; female carriers show manifestation usually, worsens with each generation (Sherman paradox) so grandfather was prob not affected, mother was mildly, grandson has full blown dz |
| example of trinucleotide repeat disorder | affects coding region - Huntington dz |
| mitochondrial disorder | COMPLETE maternal transmission; organs that use oxidative phosphorylation are affected, heteroplasmy, threshold effect. ex: Leber hereditary optic neuropathy |
| heteroplasmy | tissues or entire organism harbor both mutant and WT-mitochondrial DNA |
| Prader-Willi | disorder of genomic imprinting & microdeletion syndrome; mother has imprinted (silenced by methylation) chr 15 so when dad passes down chr 15 with microdeletion in that region + mom's silenced chr 15, dz develops |
| Angelman syndrome | disorder of genomic imprinting & microdeletion syndrome; father has imprinted (silenced by methylation) chr 15 so when mom passes down chr 15 with microdeletion in that region + dad's silenced chr 15, dz develops |
| indications for prenatal genetic testing | advanced maternal age, parent has chr aberration, prev child with one, sono-detected abnormalities, parent is carrier of an X-linked disorder |
| indications for postnatal genetic testing | multiple congenital anomalies, MR/developmental delay, suspected autosomal numerical or structural or sex chr aberration, suspected fragile X, infertility, multiple spontaneous ab or FMHx of miscarriages |
Created by:
sirprakes
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