Question

Photosynthetic eukaryotes have genes for rRNA in their nuclei, mitochondria, and chloroplasts. Based on what you know about the origins of mitochondria and chloroplasts, which of the statements below would best describe the evolutionary relationship between the rRNA genes found in these three organelles?

a. Mitochondrial, chloroplast, and nuclear rRNA are all derived from distant relatives.

b. There is no reason to assume that any of the three rRNA genes are similar to closely or distantly related relatives.

c. Mitochondrial and chloroplast rRNA are derived from close relatives; however, both are distant from nuclear rRNA.

d. Nuclear and chloroplast rRNA are derived from close relatives; however, both are distant from mitochondrial rRNA.

e. Nuclear and mitochondrial rRNA are derived from close relatives; however, both are distant from chloroplast rRNA.

Answer 1

Correct ans is a. Mitochondrial ,chloroplast and nuclear rRNA are all derived from distant relatives.

Basically, chloroplasts rRNA are derived from cyanobacteria. This consists of large subunit of 50S and small subunit of 30S which contains rRNA. It consist of about 120 genes in a circular chromosome.

Mitochondrial rRNA are derived i.e originated from eubacterial species i.e eubacterial ancestor. They are found to contain 16S and 12S sununits along with 4 types of subunits (28S,5.8S,18S and 5S) in mammals.

Nuclear rRNA are found in nucleus of proliferative cells of eukaryotes like the embryonic cells (also called cajal bodies or the coiled bodies). They are comprised of approximately 150 nucleotides. They are involved in processing of pre-messenger RNA and tend to interact with specific set of proteins.

Thus, all the three rRNA's are derived from distant relatives.