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


Reviewed May 2012

What is the official name of the KRAS gene?

The official name of this gene is “Kirsten rat sarcoma viral oncogene homolog.”

KRAS is the gene's official symbol. The KRAS gene is also known by other names, listed below.

What is the normal function of the KRAS gene?

The KRAS gene provides instructions for making a protein called K-Ras that is involved primarily in regulating cell division. As part of a signaling pathway known as the RAS/MAPK pathway, the protein relays signals from outside the cell to the cell's nucleus. These signals instruct the cell to grow and divide or to mature and take on specialized functions (differentiate). The K-Ras protein is a GTPase, which means it converts a molecule called GTP into another molecule called GDP. The K-Ras protein acts like a switch, and it is turned on and off by the GTP and GDP molecules. To transmit signals, the K-Ras protein must be turned on by attaching (binding) to a molecule of GTP. The K-Ras protein is turned off (inactivated) when it converts the GTP to GDP. When the protein is bound to GDP, it does not relay signals to the cell's nucleus.

The KRAS gene belongs to a class of genes known as oncogenes. When mutated, oncogenes have the potential to cause normal cells to become cancerous. The KRAS gene is in the Ras family of oncogenes, which also includes two other genes: HRAS and NRAS. The proteins produced from these three genes are GTPases. These proteins play important roles in cell division, cell differentiation, and the self-destruction of cells (apoptosis).

How are changes in the KRAS gene related to health conditions?

cardiofaciocutaneous syndrome - caused by mutations in the KRAS gene

Mutations in the KRAS gene are an uncommon cause of cardiofaciocutaneous syndrome, accounting for fewer than 5 percent of cases. Several mutations in this gene have been identified in people with characteristic features of the disorder, which include heart defects, distinctive facial features, and skin abnormalities. The mutations change single protein building blocks (amino acids) in the K-Ras protein. The altered protein shows increased GTP binding and a decreased ability to convert GTP to GDP. These effects lead to prolonged activation of the K-Ras protein, which alters tightly regulated RAS/MAPK signaling during development. The altered signaling interferes with the development of organs and tissues throughout the body, leading to the varied signs and symptoms of cardiofaciocutaneous syndrome.

Noonan syndrome - caused by mutations in the KRAS gene

Mutations in the KRAS gene have caused a small number of cases of severe or atypical Noonan syndrome, a condition that affects many parts of the body. Intellectual disability is more common in people who have Noonan syndrome with a KRAS gene mutation than in people with Noonan syndrome caused by a mutation in a different gene.

The KRAS gene mutations associated with Noonan syndrome change single amino acids in a critical region of the K-Ras protein. The resulting protein is overactive, with increased GTP-binding and a decreased ability to convert GTP to GDP. The abnormally active protein alters normal RAS/MAPK signaling and disrupts the development of organs and tissues throughout the body. Researchers believe that increased K-Ras activation leading to defective cell movement and differentiation could play a role in the signs and symptoms of Noonan syndrome, including short stature, heart defects, and skeletal abnormalities.

Rarely, people with Noonan syndrome caused by a KRAS gene mutation will also develop juvenile myelomonocytic leukemia, which is a type of blood cancer that typically affects children or adolescents.

cancers - increased risk from variations of the KRAS gene

Some gene mutations are acquired during a person's lifetime and are present only in certain cells. These changes, which are called somatic mutations, are not inherited. Somatic mutations in the KRAS gene are involved in the development of several types of cancer. These mutations lead to a K-Ras protein that is more strongly overactivated than the mutations that cause cardiofaciocutaneous syndrome and Noonan syndrome. The abnormal K-Ras protein is always active and can direct cells to grow and divide in an uncontrolled way. Studies suggest that KRAS gene mutations are common in pancreatic, lung, and colorectal cancers. Mutations in the KRAS gene have also been found in other types of cancer.

other disorders - caused by mutations in the KRAS gene

KRAS gene mutations also cause a disorder whose major features overlap with those of Noonan syndrome, cardiofaciocutaneous syndrome, and a related disorder called Costello syndrome. This condition has been described as the KRAS mutation-associated phenotype. People with this condition have variable signs and symptoms that include mild to moderate intellectual disability, distinctive facial features, short stature, an unusually large head (macrocephaly), and hair that is sparse and thin.

At least nine mutations in the KRAS gene have been reported in people with this disorder. Each of these mutations changes a single amino acid in the K-Ras protein. These genetic changes abnormally activate the protein, which alters chemical signaling in cells throughout the body. The altered signaling interferes with the normal development of many organs and tissues, resulting in the characteristic features of the KRAS mutation-associated phenotype.

Where is the KRAS gene located?

Cytogenetic Location: 12p12.1

Molecular Location on chromosome 12: base pairs 25,204,788 to 25,250,930

The KRAS gene is located on the short (p) arm of chromosome 12 at position 12.1.

The KRAS gene is located on the short (p) arm of chromosome 12 at position 12.1.

More precisely, the KRAS gene is located from base pair 25,204,788 to base pair 25,250,930 on chromosome 12.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about KRAS?

You and your healthcare professional may find the following resources about KRAS helpful.

You may also be interested in these resources, which are designed for genetics professionals and researchers.

What other names do people use for the KRAS gene or gene products?

  • cellular c-Ki-ras2 proto-oncogene
  • c-Kirsten-ras protein
  • C-K-RAS
  • c-K-ras2 protein
  • c-K-ras protein
  • KI-RAS
  • Kirsten rat sarcoma-2 viral (v-Ki-ras2) oncogene homolog
  • KRAS1
  • KRAS2
  • K-ras p21 protein
  • NS3
  • PR310 c-K-ras oncogene
  • RASK2
  • transforming protein p21
  • v-Ki-ras2 Kirsten rat sarcoma 2 viral oncogene homolog
  • v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding KRAS?

acids ; acute ; acute myeloid leukemia ; amino acid ; apoptosis ; atypical ; autoimmune ; biomarker ; cancer ; cell ; cell division ; class ; colorectal ; critical region ; differentiation ; disability ; gene ; GTP ; inherited ; juvenile ; juvenile myelomonocytic leukemia ; leukemia ; macrocephaly ; molecule ; mutation ; myeloid ; nucleus ; oncogene ; pancreatic ; pharmacogenetics ; phenotype ; protein ; proto-oncogene ; RAS ; RAS oncogene ; sarcoma ; short stature ; signal transduction ; stature ; syndrome ; transduction

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


  • Bell DA. Origins and molecular pathology of ovarian cancer. Mod Pathol. 2005 Feb;18 Suppl 2:S19-32. Review. (
  • Carta C, Pantaleoni F, Bocchinfuso G, Stella L, Vasta I, Sarkozy A, Digilio C, Palleschi A, Pizzuti A, Grammatico P, Zampino G, Dallapiccola B, Gelb BD, Tartaglia M. Germline missense mutations affecting KRAS Isoform B are associated with a severe Noonan syndrome phenotype. Am J Hum Genet. 2006 Jul;79(1):129-35. Epub 2006 May 1. (
  • Castagnola P, Giaretti W. Mutant KRAS, chromosomal instability and prognosis in colorectal cancer. Biochim Biophys Acta. 2005 Nov 25;1756(2):115-25. Epub 2005 Jul 13. Review. (
  • Furukawa T, Sunamura M, Horii A. Molecular mechanisms of pancreatic carcinogenesis. Cancer Sci. 2006 Jan;97(1):1-7. Review. (
  • Gremer L, Merbitz-Zahradnik T, Dvorsky R, Cirstea IC, Kratz CP, Zenker M, Wittinghofer A, Ahmadian MR. Germline KRAS mutations cause aberrant biochemical and physical properties leading to developmental disorders. Hum Mutat. 2011 Jan;32(1):33-43. doi: 10.1002/humu.21377. Epub 2010 Dec 9. (
  • Nava C, Hanna N, Michot C, Pereira S, Pouvreau N, Niihori T, Aoki Y, Matsubara Y, Arveiler B, Lacombe D, Pasmant E, Parfait B, Baumann C, Héron D, Sigaudy S, Toutain A, Rio M, Goldenberg A, Leheup B, Verloes A, Cavé H. Cardio-facio-cutaneous and Noonan syndromes due to mutations in the RAS/MAPK signalling pathway: genotype-phenotype relationships and overlap with Costello syndrome. J Med Genet. 2007 Dec;44(12):763-71. Epub 2007 Aug 17. (
  • NCBI Gene (
  • Niihori T, Aoki Y, Narumi Y, Neri G, Cavé H, Verloes A, Okamoto N, Hennekam RC, Gillessen-Kaesbach G, Wieczorek D, Kavamura MI, Kurosawa K, Ohashi H, Wilson L, Heron D, Bonneau D, Corona G, Kaname T, Naritomi K, Baumann C, Matsumoto N, Kato K, Kure S, Matsubara Y. Germline KRAS and BRAF mutations in cardio-facio-cutaneous syndrome. Nat Genet. 2006 Mar;38(3):294-6. Epub 2006 Feb 12. (
  • Pérez-Mancera PA, Tuveson DA. Physiological analysis of oncogenic K-ras. Methods Enzymol. 2006;407:676-90. (
  • Quezada E, Gripp KW. Costello syndrome and related disorders. Curr Opin Pediatr. 2007 Dec;19(6):636-44. (
  • Romano AA, Allanson JE, Dahlgren J, Gelb BD, Hall B, Pierpont ME, Roberts AE, Robinson W, Takemoto CM, Noonan JA. Noonan syndrome: clinical features, diagnosis, and management guidelines. Pediatrics. 2010 Oct;126(4):746-59. doi: 10.1542/peds.2009-3207. Epub 2010 Sep 27. Review. (
  • Schubbert S, Bollag G, Lyubynska N, Nguyen H, Kratz CP, Zenker M, Niemeyer CM, Molven A, Shannon K. Biochemical and functional characterization of germ line KRAS mutations. Mol Cell Biol. 2007 Nov;27(22):7765-70. Epub 2007 Sep 17. (
  • Schubbert S, Zenker M, Rowe SL, Böll S, Klein C, Bollag G, van der Burgt I, Musante L, Kalscheuer V, Wehner LE, Nguyen H, West B, Zhang KY, Sistermans E, Rauch A, Niemeyer CM, Shannon K, Kratz CP. Germline KRAS mutations cause Noonan syndrome. Nat Genet. 2006 Mar;38(3):331-6. Epub 2006 Feb 12. Erratum in: Nat Genet. 2006 May;38(5):598. (
  • Tidyman WE, Rauen KA. Mutational and functional analysis in human Ras/MAP kinase genetic syndromes. Methods Mol Biol. 2010;661:433-47. doi: 10.1007/978-1-60761-795-2_27. (
  • Zenker M, Lehmann K, Schulz AL, Barth H, Hansmann D, Koenig R, Korinthenberg R, Kreiss-Nachtsheim M, Meinecke P, Morlot S, Mundlos S, Quante AS, Raskin S, Schnabel D, Wehner LE, Kratz CP, Horn D, Kutsche K. Expansion of the genotypic and phenotypic spectrum in patients with KRAS germline mutations. J Med Genet. 2007 Feb;44(2):131-5. Epub 2006 Oct 20. (


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: May 2012
Published: September 1, 2015