Genetics 2 Flashcards
Multiple CGG trinucleotide repeats are present in the 5’ noncoding region of the fragile X gene (_______)
FMR1
During female meiosis _______ alleles can expand to 200-3,000 repeats in fragile X
Premature
Highest # of repeats correlates with absence of _______ and presence of fragile X
FMR1 mRNA
_______ abundant in brain and testes
FMR1 mRNA
Aberrant ______ of FMR1 promoter causes a reduction of mRNA seen in affected males with fragile X
Methylation
Has been shown to be a nucleo-cytoplasmic shuttling protein that selectively binds to a subset of mRNAs
FMR protein
Has a role in postnatal brain development and dendrite maturation in animal models. Plays a role in prenatal and postnatal brain development in humans
FMR1
Huntingtons, myotonic dystrophy, fragile X, and spinocerebellar ataxia type 1 all have
Anticipation
Huntingtons, spinocerebellar ataxia type 1, and X-linked spinal and bulbar muscular atrophy have expansions in
Father
Fragile X syndrome expansions in
Mother
Fragile site FRAXE and myotonic dystrophy can have expansions in
Either parent
Worsening of disease over several generations. Decrease in age of onset, increase in severity, increase in penetrance
Anticipation
May also stem from ascertainment vial. Mildly affect ppl may escape detection and give rise to artificially low penetrance in an older generation
Anticipation
AD. Myotonia, ptosis, cataracts, hypogonadism, frontal balding, ECG changes.
Myotonic dystrophy
Defect is amplified trinucleotide repeat in 3’ untranslated region of protein kinase gene on Chr 19
Myotonic dystrophy
Range of phenotypic manifestations of same genetic d/o, or phenotype
Variable expressivity
Refers to presence of absence of phenotype
Penetrance
Rectus to degree of manifestation of a disease that is penetrant
Variable expressivity
Neurofibromatosis can exhibit
Variable expressivity
Variability of the NF1 _______, even in families with the same NF1 gene mutation, suggests other factors are involved in determining the disease manifestation
Phenotype
Variable phenotype in those with the same NF1 mutation is a case of
Polygenic inheritance in expressivity
X-linked dominant trait with incomplete penetrance
Fragile X
Obesity, hyperphagia, intellectual disability, hypogonadism, small hands and feet. Only maternal 15q
Prader-willi
Severe intellectual disability, spasticity, and seizures. Only paternal 15q
Angelman
Multiple genes, no environment
Polygenic inheritance
Environmental and genetic factors combine to produce a phenotype
Multifactorial
