Jack and Jill’s son Jake has a severe case of myclonic epilepsy and ragged-red fiber (MERRF) syndrome. His case includes frequent and disabling myclonic seizures (involuntary twitching of the muscles) along with hearing loss, exercise intolerance, and poor night vision. Like most cases of MERRF, his case is associated with a mitochondrial mutation that he inherited from his mother Jill. His mother doesn’t know that she harbors the MERRF mutation among her mtDNA molecules, but she has experienced occasional mild muscle twitching throughout her life and she does not see very well at night. What is/are the MOST likely explanation(s) for the difference in the severity of MERRF between Jake and his mother? (Select all that apply.) The expression pattern of the mutant gene may be different in males than in females. Heteroplasmy for mtDNA molecules in the cells of his mother is responsible. Some random mutations took place in Jack’s mitochondria, which caused MERFF syndrome as his mother does not have full symptoms. It is likely that Jake has a higher proportion of mutant mtDNA molecules in his cells compared to his mother.
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