Correct option is A
Explanation-
Statement A: The bacterial ribosome consists of small and large subunits of 30S and 50S respectively, whereas in mitochondria of mammals these subunits are of 28S and 39S - CORRECT
Bacterial ribosomes are 70S particles composed of 30S (small) and 50S (large) subunits. Mitochondrial ribosomes in mammals (mitoribosomes) are 55S, comprising 28S (small) and 39S (large) subunits. This statement is accurate regarding both systems.
Statement B: In the bacterial ribosomes the RNA: protein ratio is about 2:1 whereas in mitochondria ribosomes this ratio is usually 1:2 - CORRECT
Bacterial ribosomes are RNA-rich, with more RNA than protein (hence, ~2:1 RNA:protein ratio). Mammalian mitochondrial ribosomes are protein-rich, with an RNA:protein ratio closer to 1:2 . Therefore, this statement is factually correct.
Statement C: Both the bacterial and mitochondrial ribosomes consist of 30S and 50S subunits - INCORRECT
While bacterial ribosomes are indeed 30S + 50S, mitochondrial ribosomes are 28S + 39S in mammals. This statement incorrectly generalizes mitochondrial subunit sizes, hence it is not correct.
Statement D: Both the bacterial and mitochondrial ribosomes consist of RNA and protein in the ratio of 1:1 - INCORRECT
As explained in statement B, the RNA:protein ratios differ:
Bacteria: RNA > protein (~2:1)
Mitochondria: Protein > RNA (~1:2)
Therefore, this statement is factually incorrect.
Correct Option: a (A and B only)
