Both mitochondria and chloroplasts contain their own ribosomes.A photosynthetic eukaryotic cell possesses three different types of rRNA that are similar to rRNAs from three distantly related ancestors.Which process would be consistent with this condition?
A) Secondary endosymbiosis of a chloroplast
B) Primary endosymbiosis of a mitochondrion and a chloroplast
C) Primary endosymbiosis of a chloroplast
D) Secondary endosymbiosis of a nucleus
E) Primary endosymbiosis of a mitochondrion

Question

Quizplus · Accepted Answer

The presence of three different types of rRNA indicates that the cell underwent primary endosymbiosis of a mitochondrion and a chloroplast. This is because mitochondria and chloroplasts have their own ribosomes, which are similar in structure and composition to bacterial ribosomes. Therefore, it is likely that the three types of rRNA found in the photosynthetic eukaryotic cell are derived from the ribosomes of the bacteria that were originally engulfed by the ancestral eukaryotic cell, which gave rise to both the mitochondrion and the chloroplast. This process is known as primary endosymbiosis. Secondary endosymbiosis, on the other hand, involves one already-existing endosymbiotic organism being engulfed by another organism. This would not account for the presence of three different types of rRNA in the cell.

Both Mitochondria and Chloroplasts Contain Their Own Ribosomes