The T-arm or T-loop is a specialized region on the tRNA molecule which acts as a special recognition site for the ribosome

Ribosome

A ribosome is a component of cells that assembles the twenty specific amino acid molecules to form the particular protein molecule determined by the nucleotide sequence of an RNA molecule....

 to allow a tRNA-ribosome complex to form during the process of protein biosynthesis

Protein biosynthesis

Protein biosynthesis is the process in which cells build or manufacture proteins. The term is sometimes used to refer only to protein translation but more often it refers to a multi-step process, beginning with amino acid synthesis and transcription of nuclear DNA into messenger RNA, which is then...

.

The T-arm has two components to it; the T-stems and the T-loop.

• There are two T-stems of five base pairs each. T-stem 1 is from 49-53 and T-stem 2 is from 61-65.
• The T-loop is also often known as the TΨC arm due to the presence of thymidine
  Thymidine
  Thymidine is a chemical compound, more precisely a pyrimidine deoxynucleoside. Deoxythymidine is the DNA nucleoside T, which pairs with deoxyadenosine in double-stranded DNA...
  
  , pseudouridine
  Pseudouridine
  Pseudouridine is the C-glycoside isomer of the nucleoside uridine, and it is the most prevalent of the over one hundred different modified nucleosides found in RNA. Ψ is found in all species and in many classes of RNA except mRNA...
  
   and cytidine
  Cytidine
  Cytidine is a nucleoside molecule that is formed when cytosine is attached to a ribose ring via a β-N1-glycosidic bond...
  
   residues. tRNA is the only RNA
  RNA
  Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....
  
   species that contains the nucleoside thymidine.

Organisms with T-loop lacking tRNA exhibit a much lower level of aminoacylation

Aminoacylation

Aminoacylation is the process of adding an aminoacyl group to a compound.-See also:*Acylation*tRNA aminoacylation*Transfer RNA-like structures...

 and EF-Tu-binding than in organisms which have the native tRNA.

In Mammalian DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

, telomeric repeat-binding factor 2 or TRF2 has been found to remodel linear telomeric DNA into large T-loops.