Non-Mendelian Patterns and Epigenetics

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inherit both chromosomes of a homolog from same parent
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Terms in this set (35)
when do sister chromatids separate in mitosisduring division phasephases of mitosis-prophase -metaphase -anaphase -telophase -cytokinesisMeiosis characteristics (gametes)-one replication phase and 2 division phases -DNA/chromosome replication gives rise to identical sister chromatids -final products have 23 chromosomes -homologous chromosomes pair and then separate to opposite poles in first divisionwhen do sister chromatids separate in meiosissecond divisionDoes genetic recombination occur between homologs in meiosis-yes -exchange of material in meiosis I (if not recombination can lead to problems) which helps then alignHow does UPD happen-sometimes meiotic erros -usually fetus originally trisomic and then lose a chromosome to become disomicform of gene marking thats reversiblegenomic imprintingcan epigenetic mark be heritable?yes -imprintingT/F: genomes inherited from mom an dad are not functionally equivalenttrue (imprinting)why get PWS still if normal chromosome derived from mom-imprinting: mothers genes are shut off -Need normally expressed genes in Chr15 of dad to not have PWSPWS recurrence risk-deletions and UPD: less than 1 percent (usually de novo deletions and UPD rare) -Imprinting error: can be 50% (error may be heritable mutation present in parent)whats UBE3A (E6-AP)ubiquitin protein ligase gene on chromosome 15 (mutated in angel man sometimes)imprinting mechanism-occurs before fertilization -confers txn silencing of maternal or paternal allele -stable when transmitted through mitosis in somatic cells -must be reversible on passage through opposite sex -can impact inheritance patternDNA that codes for some genes important for mitochondria function and oxidative phosphorylationmtDNAinheritance of mtDNA-maternal inheritance (diseases from mutated mtDNA passed from female to offspring only)mutation rate of mtDNA10-100x greater than nucleus due to lack of proofreading and DNA-repairmtDNA diseases-disorders of ox.phosphorylation, FA oxidation, etc -LHON (leber hereditary optic neuropathy) -MERRF (myclonic epilepsy with ragged red fibers) -MELAS (mt encephalomyopathy, lactic acidosis and stroke-like episodes) -Leigh Syndrome and NARP (later in life) -Deafnessmost common clinical finding for mtDNA diseasesneurologic problemcauses of mtDNA diseases-Genetic defects (point mutations, deletions, duplications, etc) -De novo mutations (no family history) -Accumulation of mutations with age (high mutation rate and low repair)whats homoplasmy and heteroplasmy in mtDNAHomoplasmy: MtDNA genomes of cell the same heteroplasmy: MtDNA genomes more than one type (ex: mutant and wild type)how is mtDNA sortedrandomly -then cell divides and mt distribute randomly between 2 daughter cells (replicative segregation)threshold effect in mtDNA-if end up with many mutant mitochondria may see phenotypic expression -depends on tissue -phenotype may vary with timewhat does threshold effect lead to-Reduced penetrance -variable expressivity -pleiotropygenetic bottleneck-heteroplasmic females transmit some mutant mtDNAs - # mtDNA reduced then amplified in mature oocyte (bottleneck) -can lead to variability in % offspring with mutant mtDNAleber hereditary optic neuropathy (LHON)-blindness due to optic nerve atrophy (mainly central vision) -visual acuity reduced -most people have point mutation of mtDNA (largely homoplasmic) -complicated by gender and age dependent penetrance