Question

researchers have found that mitochondria and chloroplasts in eukaryotic cells have their own dna. this dna is different from the dna in a eukaryotic cells nucleus. chloroplasts and mitochondria use their own dna and ribosomes to make some organelle - specific proteins. what statement is best supported by this information? a. mitochondria and chloroplasts could exist outside of modern cells. b. modern cells could exist without mitochondria and chloroplasts. c. early eukaryotic cells engulfed prokaryotic cells, which later became mitochondria and chloroplasts. d. early prokaryotic cells engulfed eukaryotic cells, which later became mitochondria and chloroplasts.

Explanation:

The endosymbiotic theory states that mitochondria and chloroplasts were once free - living prokaryotes. Early eukaryotic cells engulfed these prokaryotes (mitochondria - like and chloroplast - like). Over time, a symbiotic relationship developed. If mitochondria and chloroplasts could exist outside of modern cells (as stated in option A), it would support the idea that they were once independent organisms (a key aspect of the endosymbiotic theory). Option B is incorrect because modern cells cannot exist without mitochondria (they are essential for energy production in most eukaryotic cells). Option C has the engulfing order wrong (early eukaryotic cells engulfed prokaryotes, not the other way around). Option D also has the cell type wrong (it was early eukaryotic cells that engulfed prokaryotes, not early prokaryotic cells engulfing eukaryotic cells).

Answer:

A. Mitochondria and chloroplasts could exist outside of modern cells.