{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"T-cell receptor alpha locus is a protein that in humans is encoded by the TRA gene, also known as TCRA or TRAα; It contributes the alpha chain to the larger TCR protein (T-cell receptor). The T cell receptor or TCR is a molecule found on the surface of T lymphocytes (or T cells) that is responsible for recognizing antigens bound to major histocompatibility complex (MHC) molecules. The TCR is composed of two different protein chains (that is, it is a heterodimer). In 95% of T cells, this consists of an alpha (α) and beta (β) chain, whereas in 5% of T cells this consists of gamma and delta (γ/δ) chains. This ratio changes during ontogeny and in cancers, such as Leukemia."}]}]}