Question

Which of these cellular structures would be found in all living cells across all domains on earth and can indicate common ancestry?

A)ChloroplastsB)CiliaC)MItochondriaD)Ribosomes

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Answer 1

Ribosomes is the answer

Answer 2

The correct answer is : D) Ribosomes.

Explanation:

• Ribosomes are protein synthesising machinery of the cells.
• They are accountable for Translation.
• Translation refers to the process by which the codons encoding amino acids present on the mRNA (messenger RNA) is read by the ribosome and according a polypeptide chain is synthesised.
• Ribosomes are present in all living organisms on earth (except, viruses, viriods, prions which hijack the host cell's machinery for self renewal).
• Prokaryotes have 70S  ( 50S and 30S subunit ) ribosome.
• Eukaryotes have 80S ( 60S and 40S subunit ) ribosome.
• Here 'S' stands for Svedberg unit which measures the sedimentation co-efficient, that is, the centrifugation speed at which the subunits will sediment down.
• The presence of ribosomes across the diverse domains, Bacteria, Archaea and Eukaryota indicates that it was derived from a common ancestor.