Genes of a single-celled organism and the genes of a multi-cellular

[Therian]

What is the difference between the genes of a single-celled organism and the genes of a multi-cellular organism? I mean could the genes of a single celled organism be used in a certain way in a multi-cellular organism?

Thanks

 

[LeonhardEuler]

It depends on the type of single celled organism. Procaryotes are more primitive and, by definition have their DNA free in the cytoplasm. It is usually in one large circular piece, while smaller circular rings, called plasmids may also be present. Eukaryotes, a class to which all multicellular, and some single celled organisms belong, have the DNA in the nucleus. The DNA works basically the same way in both multicellular and single celled organisms. In fact, insulin for diabetics is now produced by creating a plasmid for the gene that makes insulin and inserting it into single celled organisms. I don't know of an example of a single celled organism's DNA being used in a multicellular organism, but it certainly seems plausible.

 

[Therian]

okay well my friend mentioned a while ago that there were single-celled organisms or something that joined together to form one organism could somebody shed some light about things like those and their genes and whether or not their genes could be used in multi-cellular organisms

Thanks

 

[LeonhardEuler]

It is true that multi-cellular organisms evolved from single celled ones. It is not easy to say exactly where single celled organisms end and multicellular ones begin. You have organisms which are certainly single celled, like parameciums. Then you have algae that group together in amorphous blobs. Then you have other algae, such as Volvox, which group togerther in sherical colonies. Here there is organisation, but not specialization: all the cells are the same. Then you have an organism like the Hydra which exhibits both organisation and specialization: Some cells are specialized to sting prey, others are specialized as epidermal tissue, etc. In full fleged multicellular organisms, cells are always specialized (with the exception of embryonic stem cells). Eye cells are different from liver cells, which are different from neurons etc.. While all of these cells (with the exception of the gametes) have all of the organisms DNA, various protiens in the nucleus supress or enhance the transcription of different parts of the DNA. This is the difference between different kinds of cells: which genes are "on". This constitutes another difference between sigle and multi-cellular organisms: all of the genes in the one cell of a single celled organism can potentially go "on".

 

[iansmith]

Then you have other algae, such as Volvox, which group togerther in sherical colonies. Here there is organisation, but not specialization: all the cells are the same.

Volvox might not be the best example of not specialization. Most of the colony has a flagella and are in non-reproductive. A minority has no flagella and the purpose is to reproduce. There is limited specialization in volvox. Volvox could be view as the middle man between no specilization to full specialization and organisation