3: Mitochondrial Genome

which organelle evolved from bacteria that were engulfed by an ancient eukaryotic cell?

mitochondria

what are the structural features of the human mitochondrial genome?

a very small, circular, double-stranded DNA with no introns

what is the process by which mtDNA is passed down?

maternal inheritance

why do sperm not contribute mitochondria to a zygote?

sperm mitochondria do not enter the zygote or are destroyed during fertilization

what is the term for a cell or tissue containing both normal and mutant mtDNA?

heteroplasmy

what is the “threshold effect”?

the percentage of mutant mtDNA must exceed a specific level before clinical signs of disease appear

what explains the variability in clinical manifestations of an mtDNA mutation among different individuals?

heteroplasmy and the threshold effect

what is the term for multiple, seemingly unrelated phenotypic effects caused by a mutation in a single gene?

pleiotropy

what are some factors that contribute to the higher mutation rate of mtDNA compared to nuclear DNA?

• mtDNA lack protective histones

• mtDNA have no introns

• mitochondria have inefficient DNA repair

• mtDNA is exposed to oxygen free radicals generated by oxidative phosphorylation

what cellular process are the 13 proteins encoded in the mitochondrial genome involved in?

electron transport and oxidative phosphorylation