Evolution Trivia Quiz

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7. Mitchondria doing what they do

Storing genetic information is the function of DNA, most of which is found in the chromosomes of the cell nucleus. Some DNA is also found outside the cell nucleus in the mitochondria, small rod-shaped bodies found in most cells of the body in humans and other animals. What is the main function of mitochondria?

A) To help seal off toxins and protein fragments that could impair the cell
B) To maintain the salinity and moisture content of the cell at optimum levels
C) To provide the chemical energy that powers cellular processes
D) To serve as a genetic back-up when key genes in the nucleus are damaged

Your answer — B) To maintain the salinity and moisture content of the cell at optimum levels — was incorrect.

Each cell can contain up to two thousand mitochondria depending on its energy needs. A few cell types, like red blood cells, do not contain mitochondria at all. It is believed that mitochondria originated about a billion years ago from one or many occasions on which an independent bacterial cell invaded or was absorbed by a host cell and took up residence there. The quantity of DNA in each mitochondrion is small, amounting in humans to only thirty-seven genes; human nuclear DNA, in contrast is thought to encode about twenty thousand genes. Interestingly, mitochondrial DNA comes from one’s mother only, unlike nuclear DNA to which both parents contribute. It has been suggested that the greater longevity of females is due at least in part to this exclusively female control of the mitochondrial genome.

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