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24 Cards in this Set
- Front
- Back
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variable expressivity
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-refers to the ability of one genetic mutation to present with different phenotypes among individuals
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penetrance
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-the ability of a genetic mutation to be expressed
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Marfan syndrome
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-an autosomal dominant disorder
-thought to be due to a mutation in the gene that encodes fibrillin-1 -men and women affected equally -multisystem organ involvement is observed -Diagnosis requires 1 “major” and 1 “minor” manifestation in a patient with a first degree relative known to carry the diagnosis -Diagnosis without a family history requires major manifestations in 2 organ systems and 1 minor manifestation in a third organ system |
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marfan syndrome clinical manifestations
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-near sighted
-eye lens dislocation -retinal detachment -spont lung collapse -aorta widening or dilatation -aortic aneurysms -mitral and/or aortic valve prolapse -curvature of the spine -pigeon chest -tall -loose jointedness |
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B-thalassemia major
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-heme is the protein in RBCs that is responsible for carrying O2 to peripheral tissues
-when there is a problem with the production of heme anemia can result -heme is compsed of 2alpha and 2 beta chains (defect in Bgene) -inheritance of an abnormal recessive gene from each parent results in B-thalassemia, a chronic anemia that fosters dependence on transfusion therapy |
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in many cases, for B thalassemia, the mutation is...
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-within the protein itself, while in B+ thalassemia, the mutation is within the promotor region
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B thalassemia major tx
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-chronic transfusion therapy
-give pt a functional gene |
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x-linked disorders
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1. hemophilia A
2. duchenne muscular dystrophy 3. becker muscular dystrophy 4. red-green color blindness 5. menkes syndrome |
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mitochondrial disorders
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-a maternally derived form of inheritance in which aberrations in mitochondrial DNA are responsible for the observed phenotype
-Since only ova transmit mitochondrial DNA, fathers cannot transmit this genetic mutation to offspring |
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types if mitochondrial disorders
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1. Myoclonic epilepsy and red-ragged fibers
2. mitochondrial encephalopathy and lactic acidosis: stoke like episodes and lactic acidosis 3. Leigh disease: basal ganglia defects, hypotonia, optic atophy 4. Kearns- Sayre syndrome: Opthalmoplegia,retinitis pigmentosa,myopathy,cardaic conduction defects 5. Pearson syndrome: Anemia,neutropenia,pancreatic dysfunction,myopathy |
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Genomic imprinting
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-refers to the differences in gene expression,depending on whether a mutated allele is transmitted from the maternal or paternal genome
-If the mutated allele is transmitted from the father, there is a different phenotype than if it was transmitted by the mother |
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Uniparental disomy
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-a condition in which both
copies of a chromosome are from one parent. This is caused by nondisjunction of a chromosome during meiosis |
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Prader willi syndrome
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-hypotonia
-obesity -mental retardation -small hands and feet -deletion of paternally active genes on chr 15 |
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Angelman syndreom
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-mental retardation
-hand flapping -ataxia -puppet like gait -deletion of maternally active genes on ch 15 |
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Trisomy 21
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-most common autosomal chromosome abnormality in humans
-94% are due to 3 copies of the whole chromosome 21(from nondisjunction), with others consisting of 3 copies of the long arm as a result of translocations, and yet others are mosaics -mom >35 risk factor |
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trisomy 21 features
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1. hypotonia
2. small ears 3. mental retardation 4. bradydactyly 5. small nipple buds 6. simian crease 7. epicanthal folds 8. high arched palate 9. flat midface 10. hypoplasia of the middle phalanx of the 5th digit 11. congenital heart dz |
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Trisomy 18
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-3rd most common autosomal disorder
-girls 4x more affected than boys -95% are due to 3 copies of chromosome 18, while the remaining 5% are due to mosaicism or partial trisomy of the long arm of 18 |
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trisomy 18 features
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1. IUDR
2. mental retardation 3. microcephaly 4. rocker bottom feet 5. club foot/clenched fist 6. VSD 7. hypoplastic nails |
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deletion syndromes
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-result from missing chromosomal material
-If a deletion comes from the short arm of a chromosome it is termed p-, whereas if it comes from the long arm of a chromosome, it is termed q- -most deletion syndromes have mental retardation -Microdeletion syndromes result from small chromosomal deletions, which can be detected using FISH—fluorescence in situ hybridization |
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5p (Cri-du-chat)
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1. widely spaced eyes
2. moon face 3. short stature 4. hypotonia 5. microcephaly 6. wide and flat nasal bridge 7. mental retardation 8. "cats cry" due to laryngeal abnormalities |
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7q11.23 (Williams syndrome)
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1. round face with periorbital fullness
2. strabismus 3. supravalvular aortic stenosis 4. mental retardation 5. "cocktail personality" |
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Turnoer syndrome
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-XO
1. phenotypically female 2. short stature 3. absence of menses/ovarian failure 4. bicuspid aortic valve 5. coarctation of the aorta 6. broad webbed neck 7. edema 8. low posterior hair line 9. shield shaped chest |
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Klinefelter syndrome
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-47 XXY
-most common sex chromosome abnormality in males -meiotic nondisjunction of the x chromosome - |
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klinefelter features
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1. mental retardation
2. psyc problems 3. tall, slim, underweight at onset of puberty 4. above nml final height 5. hypogonadism 6. infertility/azoospermia |
