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70 Cards in this Set
- Front
- Back
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Define codominance
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Neither of 2 alleles are dominant
e.g. blood groups |
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Define pleiotropy
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A gene having multiple effects on phenotype
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Define imprinting
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A difference in phenotype based on whether a gene is from maternal or paternal origin
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What is anticipation?
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Worsening of a hereditary disease or earlier age of onset in successive generations (e.g. Huntington's)
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Loss of heterozygosity must occur with what type of genes to cause cancer?
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Tumor suppressor genes
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What is a dominant negative mutation?
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A mutation that produces a mutated protein which, in a heterozygote, also inhibits the product of the normal allele.
e.g. DNA-binding Tx factor |
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What is linkage disequilibrium?
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The tendency for alleles at 2 linked loci to occur together more commonly than by chance; on a population scale
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What is lyonization?
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Random inactivation of one X chromosome in females causing them to be mosaics
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What is a genetic chimera?
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A single individual derived from 2 zygotes that fused in utero, with cell lines of multiple genotypes
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What is locus heterogeneity?
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When the same phenotype is produced by mutations at different loci
e.g. albinism e.g. Marfan's = MEN 2B = homocystinuria with regards to the marfanoid habitus |
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What is heteroplasmy?
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The presence of both normal and mutated mtDNA --> variable expressivity of mitochondrial inherited disease
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What is uniparental disomy?
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When both copies of an offspring's chromosome come from only 1 parent
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What is a dominant negative mutation?
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A mutation that produces a mutated protein which, in a heterozygote, also inhibits the product of the normal allele.
e.g. DNA-binding Tx factor |
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What are the conditions necessary for Hardy-Weinberg equilibrium?
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1. No new mutations at the locus
2. No selection for any of the genotypes at the locus 3. Random mating 4. No migration |
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What is linkage disequilibrium?
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The tendency for alleles at 2 linked loci to occur together more commonly than by chance; on a population scale
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What chromosome hold the genes for Prader-Willi and Angelman syndromes?
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Chromosome 15
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What is lyonization?
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Random inactivation of one X chromosome in females causing them to be mosaics
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What is a genetic chimera?
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A single individual derived from 2 zygotes that fused in utero, with cell lines of multiple genotypes
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What are the cause and features of Prader-Willi syndrome?
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Deletion of the active paternal allele
--> retardation, hyperphagioa and obesity, hypogonadism, hypotonia |
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What is locus heterogeneity?
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When the same phenotype is produced by mutations at different loci
e.g. albinism e.g. Marfan's = MEN 2B = homocystinuria with regards to the marfanoid habitus |
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What is heteroplasmy?
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The presence of both normal and mutated mtDNA --> variable expressivity of mitochondrial inherited disease
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What is uniparental disomy?
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When both copies of an offspring's chromosome come from only 1 parent
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What are the conditions necessary for Hardy-Weinberg equilibrium?
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1. No new mutations at the locus
2. No selection for any of the genotypes at the locus 3. Random mating 4. No migration |
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What chromosome hold the genes for Prader-Willi and Angelman syndromes?
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Chromosome 15
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What are the cause and features of Prader-Willi syndrome?
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Deletion of the active paternal allele
--> retardation, hyperphagioa and obesity, hypogonadism, hypotonia |
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What are the cause and features of Angelman's syndrome?
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Mutation of the active maternal allele
--> retardation, seizures, ataxia, inappropriate laughter (happy puppet) |
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What is the inheritance pattern of hypophosphatemia rickets?
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X-linked dominant
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What is a histologic feature of mitochondrial myopathies?
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ragged red muscle fibers
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What is the mutation and inheritance pattern for achondroplasia?
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Defect of FGF receptor 3
autosomal dominant |
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What is the most common mutation in autosomal dominant polycystic kidney disease?
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PKD1 on chromosome 16
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What is associated with AD polycystic kindey disease?
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berry aneurysms*
polycystic liver mitral valve prolapse |
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What is the mutation and inheritance pattern of FAP
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Chromosome 5 APC gene (5 letters in polyp)
autosomal dominant |
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What is hereditary hemorrhagic telangiectasia/Osler-Weber-Rendu syndrome?
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AD inherited blood vessel disorder
telangiectasia, recurrent epistaxis (nosebleeds), skin discoloration, AVMs |
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What is hereditary spherocytosis and how is it treated?
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Defect in spectrin or ankyrin --> spheroid erythrocytes, hemolytic anemia, increased MCHC
AD inheritance cured with splenectomy |
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How is Huntington's disease inherited?
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trinucleotide repeats in gene on chromosome 4 (Hunting 4 food!)
autosomal dominant |
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What are the features of Huntington's?
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depression, dementia, choreiform movements, caudate atrophy, low GABA and ACh in the brain
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What happens to the aorta in Marfan's?
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Cystic medial necrosis --> aortic incompetence and dissecting aneurysms
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What gene is associated with MEN 2A and 2B?
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ret
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What is the location of the locus for neurofibromatosis 1/von Recklinhausen's disease?
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chromosome 17q
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What are features of neurofibromatosis 1?
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cafe-au-lait spots, neural tumors, Lish nodules )pigmented iris hamartomas), scoliosis, optic nerve gliomas
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What are features of neurofibromatosis 2?
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bilateral acoustic schwannomas
juvenile cataracts |
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Where is the locus for neurofibromatosis 2?
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NF2 on 22!
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What are features of tuberous sclerosis?
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facial lesions: adenoma sebaceum
ash-leaf spots (hypopigmented macules) cortical/retinal hamartomas seizures retardation renal cysts and angiomyolipomas cardiac rhabdomyomas astrocytomas |
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What is a hamartoma?
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A non-neoplastic malformation, growing at the rate of surrounding tissues, that consists of disorganized site-appropriate tissue elements
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What are features of von Hippel-Lindau disease?
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hemangioblastomas of retina, cerebellum, medulla
multiple bilateral renal cell carcinomas, etc. in 50% |
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What is the genetic basis of von Hippel-Lindau disease?
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VHL gene deletion from 3p --> constituitive expression of HIF transcription factor and activation of angiogenic growth factors
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When does autosomal recessive polycystic kidney disease present?
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In infancy
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What is the genetic basis for cystic fibrosis?
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CFTR gene mutation (Phe 508 deletion) on 7 --> abnormal folding
loss of secretion of Cl into lungs and GI tract --> mucus in lungs, pancreas, liver |
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What pulmonary infections does cystic fibrosis predispose to?
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Pseudomonas and S. aureus
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What are features of cystic fibrosis?
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chronic bronchitis
bronchiectasis pancreatic insufficiency and ADEK vitamin deficiencies nasal polyps meconium ileus |
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How does N-acetylcysteine treat cystic fibrosis?
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Cleaves disulfide bonds in mucus glycoproteins
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X-linked recessives:
Be Wise Fool's G O L D Heeds Silly Hope |
Bruton's agamaaglobulinemia
Wiskott-Aldrich syndrome Fabry's disease G6PD deficiency Ocular albinism Lesch-Nyhan syndrome Duchenne's (and Becker's) muscular dystrophy Hunter's Syndrome Hemophilia A and B |
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What is the genetic basis of Duchenne's?
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frame-shift mutation of X-linked dystrophin gene --> muscle breakdown
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What are features of Duchenne's?
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Weakness beginning in pelvic girdle and progressing superiorly
Pseudohypertrophy of calves with fibrofatty replacement Cardiac myopathy Gower's maneuver |
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How are muscular dystrophies diagnosed?
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Increased creatine phosphokinase (CPK)
muscle biopsy |
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What is the genetic basis of Becker's muscular dystrophy?
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Mutation of dystrophin gene without frameshift
Less severe than Duchenne's Onset in adolescence or young adulthood |
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What is the genetic basis of Fragile X?
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X-linked defect affection methylation of FMR1
trinucleotide repeats |
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What are features of Fragile X?
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mental retardation (2nd most common after Down's)
autism X-tra large testes, jaws, ears, long faces |
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What pregnancy quad screen results indicate Down syndrome?
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low alpha-fetoprotein
low estriol high beta-HCG high inhibin A |
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What ultrasound finding indicates Down syndrome?
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increased nuchal translucency
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What are less-obvious features of Down syndrome?
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duodenal atresia
gap between toes 1 and 2 CHD after 35: acute lymphoblastic leukemia |
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What are rare causes of Down syndrome?
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Robertsonian translocation
mosaicism |
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What is a Robertsonian translocation?
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A fusion of the long arms of acrocentric chromosomes (13, 14, 15, 21, and 22) at the centromere
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What is Edward's syndrome?
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Trisomy 18
--> micrognathia (small jaw) low-set ears clenched hands rocker-feet prominent occiput CHD death by 1 year |
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What pregnancy quad screen indicates Edward's?
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low alpha-fetoprotein
low beta-HCG low estriol normal inhibin |
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What is Patau's syndrome?
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Trisomy 13
--> cleft palate holoprosencephaly polydactyly CHD retardation micropthalmia microcephaly rocker-feet death by 1 year |
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What is Cri-du-chat syndrome?
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Microdeletion of 5p
--> microcephaly retardation high-pitched cry epicanthal folds VSD |
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What is William's syndrome?
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microdeletion of 7q (including elastin gene)
--> elfin facies, retardation, hypercalcemia/Vit D hypersensitivity high verbal skills, friendliness CVD |
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Features of 22q11 deletion:
CATCH-22 |
Cleft palate
Abnormal facies Thymic aplasia --> T cell deficiency CHD Hypocalcemia (from parathyroid aplasia) |
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What is the genetic basis of velocardiofacial syndrome?
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22q11 deletion
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