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All I know about adaptor is that it is a device that converts attributes of one electrical device or system to those of an otherwise incompatible device or system. Thank you.

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    $\begingroup$ When you make a statement like "why is tRNA called an adaptor molecule" you imply that it is some kind of a definition, which it is not. I can call tRNA using any of its attributes for example "carrier molecule" or "essential molecule" etc. You can check the meaning of "adaptor" in a biological context and see why it fits for tRNA. IMO, this question has a very narrow scope. $\endgroup$ – WYSIWYG May 24 '16 at 8:49
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RNA and proteins are not electrical systems, but the idea of translating a signal between incompatible systems can be applied here.

Proteins are made through a process called Translation, where instructions stored in a piece of mRNA are used by the Ribosome to make protein.

tRNAs adapt the mRNA nucleotide sequence into a protein's peptide sequence by acting as an intermediary. A tRNA is charged by attaching an amino acid to one end, it then binds the ribosome mRNA complex at the position defined by a codon. A codon is a sequence of 3 nucleotides that codes for an amino acid.

mRNA Translation from wikipedia

You could think of the tRNA being like a SD Card to USB adaptor to get information from one device to another.

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Francis Crick published the The adaptor hypothesis in a privately circulated article (now available online) “On Protein Synthesis” in 1958. He wrote:

“One would expect, therefore, that whatever went on to the template in a specific way did so by forming hydrogen bonds. It is therefore a natural hypothesis that the amino acid is carried to the template by an ‘adaptor’ molecule, and that the adaptor is the part which actually fits on to the RNA. In its simplest form one would require twenty adaptors, one for each amino acid.”

The word ‘adaptor’ has no intrinsic electrical connotation: the Oxford English Dictionary online gives the first definition and examples for this as:

Adapter (also adaptor)

A device for connecting pieces of equipment that cannot be connected directly.

‘the adapter converts the lens focal length to 5.5 mm’

‘a tube fixed to the cleaner by means of an adapter’

Crick clearly used the word in this sense.

At that time the idea was first mooted (reportedly 1955) it was not known that the adaptor molecule was transfer RNA (tRNA), although I have labelled it as such in the illustration I have prepared for the iPhone generation.

transfer RNA as a USB adaptor

[Textual Explanation for the visually impaired

The illustration shows: 1. Chemical incompatibility: a three-pin electrical socket, labelled ‘mRNA triplet codon’, and the flat connection end of a USB cable, labelled ‘cognate amino acid’; 2. The Adaptor: an adaptor plug (labelled tRNA) with the three pins labelled ‘anticodon loop’, and the USB socket labelled ‘acceptor stem’; 3. Decoding: the USB lead connected to the adaptor plug, which has been inserted into the the three-pin socket.]

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  • $\begingroup$ Not sure why this question resurfaced, but I thought that the accepted answer did not address the analogy, and the comment fails to acknowledge the historical use of this term. I have not included a diagram of tRNA showing the key features as it is assumed the reader has encountered this already. It is available in numerous pages on line, although best read about in a book. $\endgroup$ – David Feb 7 '18 at 12:06
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The term "adaptor" does not solely refer to electrical connections. In fact, any system that can establish a connection between two otherwise incompatible systems is called an "adaptor", as you can tell from the following list:

It is just natural that the term "adaptor" has been applied to concepts in biochemistry. You can't connect an amino acid to the RNA template directly. The two incompatible systems are thus RNA and the amino acid. The tRNA solves this problem. It is also not the only case where this term is used in biochemistry. Other examples include the signal transducing adaptor proteins or the vesicular transport adaptor proteins such as adaptin, that establishes a connection between the clathrin molecule and the cargo receptors during vesicle formation:

enter image description here

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