Question

Which of the following do Archaea and Bacteria have in common?

They both use a special form of RNA polymerase to transcribe their DNA.

They both are commonly found on human skin.

They both make chitin in order to reinforce their cell membranes.

They both keep their DNA in the form of a nucleoid.

Answer 1

Archaea by their name describes a distinct domain of single celled organisms that are once thought to be closely related to prokaryotes such as bacteria. The arch prefixes signifies a advance capabilities of these organisms to survive in extreme conditions, in heat (thermophiles), salt concentrations (halophiles), high acidity (acidophiles) etc.

The reason for this extreme tolerance of environmental stress principally stems from their membrane structure. Instead of ester linkages found in the fatty acid (C double bond O and O) bilayer pseudo-membrane for bacteria, ether linkages (O single bond C single bond O) are used to link hydrocarbons to the glycerol back bone which composes the archaea cell membrane. The ether is less prone to degradation and less reactive than the ester counterpart. Additional the presence of peptidoglycan, a sugar molecule that is used as a structural unit for the cell walls is present within bacteria but not archaea. Antibiotics often target the peptidoglycan structural components in bacteria to prevent them from reproducing (penicilin), this gives majority of archaea cellular organisms immunity from antibiotics.

However from this evidence it is tempting to focus on A as the answer. But the question is asking why are they considered different by today's classification. It is because archaea organism are actually more closely related to eukaryotes (Complex single/multicellular organisms). This is because they share very similar molecular machinery to eukaryotes in there DNA replication and protein synthesis mechanisms, they have histone, nucleosome like structures for storing DNA (much similar to human cells) while bacteria usually only have circular strand of chromosome. And multiple types of transcription enzymes to preform this act while bacteria usually only have one type. It is because of this difference in reproduction mechanisms they are classified differently from bacteria and they are considered to be more closely related to us than to bacteria.

D would be the most correct answer to the question, A is a correct statement but does not provide sufficient relevant information to answer the question.

Answer 2

so, They both keep their DNA in the form of a nucleoid?

Answer 3

Yes they keep it both in the form of a nucleoid

They are both single cellular organisms with no distinct nucleus (double membrane vessel that keeps DNA separate from the rest of the stuff) or membrane bound organelle but the way that DNA is copied, stored and packaged in archaea is much more similar to eukaryotes than the way DNA it is in bacteria.

Answer 4

thanks!

Answer 5

No problem

Although I would advise you to watch out when using the term nucleoid for archaea, since nucleoid usually strictly refers to prokaryotes (bacteria) for a DNA molecule related assembly. The 'nucleiod' inside archaea should be packaged DNA with histones, but the use of nucleoid for both is debatable.