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Correct Answer: both b and c.
to understand why the correct answer to the question regarding myoclonic epilepsy and red-ragged fibers (merrf) inheritance is not mendelian, it's important to first clarify how mitochondrial dna (mtdna) inheritance differs from nuclear dna inheritance. typically, mendelian inheritance patterns arise from the nuclear dna, which is contributed by both parents and involves the segregation and independent assortment of chromosomes. in contrast, mtdna is inherited exclusively through the mother. this is because the mitochondria in sperm cells, which could contribute paternal mtdna, are usually destroyed or diluted significantly after fertilization. thus, any mutation or disease associated with mtdna, such as merrf, will be passed down only from the mother to all of her offspring, regardless of their sex.
given the maternal inheritance pattern of mtdna, the expectation in the case of merrf, assuming affected individuals can reproduce, is that all children of an affected mother have a high probability of inheriting the disease. the pattern observed here is distinctly non-mendelian because there is no influence from the father's mtdna, and the inheritance is not dependent on typical factors like dominant or recessive gene interactions that characterize mendelian genetics.
furthermore, the uniform transmission from mother to all offspring also implies that the disease's expression is not influenced by typical mendelian ratios (such as the 3:1 ratio seen in monohybrid crosses for a dominant trait). instead, the occurrence of the disease in the offspring depends solely on the mother’s mtdna, which they all inherit. this highlights the critical aspect of mitochondrial diseases: their potential to affect all children of an affected mother, making genetic counseling and understanding of inheritance patterns crucial for affected families.
in summary, the inheritance of merrf is an example of non-mendelian inheritance due to its transmission exclusively through the maternal line via mitochondrial dna. this type of inheritance pattern is fundamentally different from the mendelian inheritance observed with nuclear genes, involving no paternal contribution and affecting all offspring of the mother. therefore, the correct answer to the question is that the disease follows a non-mendelian inheritance pattern, and the mother passes the disease to all her offspring.
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