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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®

TRNA gene family

Reviewed October 2012

What are the TRNA genes?

Genes in the TRNA gene family provide instructions for making molecules called transfer RNAs (tRNAs). Transfer RNAs are a particular type of RNA, which is a chemical cousin of DNA. These molecules help assemble protein building blocks (amino acids) into functioning proteins. Each tRNA attaches to a particular amino acid. During protein assembly, the tRNA recognizes a specific three-letter sequence (a codon) in the genetic blueprint for making proteins and inserts the amino acid into the appropriate location in the growing protein.

There are two classes of tRNA: cytoplasmic and mitochondrial. Cytoplasmic tRNAs are found in the fluid inside cells (the cytoplasm). These tRNAs help produce proteins from genes located in the DNA in the nucleus of the cell (nuclear DNA). Although most DNA is nuclear, cellular structures called mitochondria have a small amount of their own DNA, called mitochondrial DNA. Proteins produced from genes located in mitochondrial DNA are assembled by mitochondrial tRNAs.

Mutations in TRNA genes reduce the ability of the tRNA to add amino acids to proteins, slowing protein production. Mutations that affect mitochondrial tRNAs impair the ability of mitochondria to provide energy for cells or to control blood sugar levels. These mutations can cause a variety of signs and symptoms, including muscle weakness, seizures, neurological problems, hearing loss, and diabetes. Mutations in genes that provide instructions for cytoplasmic tRNAs do not appear to cause disease.

Which genes are included in the TRNA gene family?

The HUGO Gene Nomenclature Committee (HGNC) provides an index of gene families ( and their member genes.

Genetics Home Reference summarizes the normal function and health implications of these members of the TRNA gene family: MT-TE, MT-TH, MT-TK, MT-TL1, MT-TS1, and MT-TV.

What conditions are related to genes in the TRNA gene family?

Genetics Home Reference includes these conditions related to genes in the TRNA gene family:

  • Leigh syndrome
  • maternally inherited diabetes and deafness
  • mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes
  • myoclonic epilepsy with ragged-red fibers
  • nonsyndromic hearing loss
  • palmoplantar keratoderma with deafness
  • progressive external ophthalmoplegia

What glossary definitions help with understanding the TRNA gene family?

acids ; amino acid ; cell ; codon ; cytoplasm ; diabetes ; DNA ; gene ; glutamic acid ; histidine ; leucine ; lysine ; mitochondria ; neurological ; nucleus ; protein ; RNA ; serine ; tRNA ; valine

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


These sources were used to develop the Genetics Home Reference summary for the TRNA gene family.

  • Rich A, RajBhandary UL. Transfer RNA: molecular structure, sequence, and properties. Annu Rev Biochem. 1976;45:805-60. Review. (
  • Suzuki T, Nagao A, Suzuki T. Human mitochondrial tRNAs: biogenesis, function, structural aspects, and diseases. Annu Rev Genet. 2011;45:299-329. doi: 10.1146/annurev-genet-110410-132531. Epub 2011 Sep 6. Review. (
  • The Cell: A Molecular Approach (second edition, 2000): Translation of mRNA (
  • Molecular Biology of the Cell (fourth edition, 2002): From RNA to Protein (
  • Biochemistry (fifth edition, 2002): Protein Synthesis Requires the Translation of Nucleotide Sequences into Amino Acid Sequences (
  • McClain WH. Transfer RNA identity. FASEB J. 1993 Jan;7(1):72-8. Review. (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: October 2012
Published: February 8, 2016