Hamilton Smith

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Hamilton Smith

Hamilton Othanel Smith (born August 23, 1931) is an American microbiologist and a Nobel prize winner. He was jointly awarded the 1978 Nobel Prize in Physiology or Medicine. He is a leader in the field of genomics.

Hamilton Smith was, with Craig Venter, a leader in the Celera corporation's bid to analyse and sell information about the human genome. The basic idea was to find ways to make DNA sequencing cheaper so that everyone could have their DNA analysed. Then the information could be used for medical purposes.

Smith's award was for the discovery of restriction enzymes. These are enzymes that cut DNA at specific places.[1][2][3] Such enzymes, found in bacteria and archaea, probably evolved to provide a defense mechanism against invading viruses.[4][5] Inside a bacterial host, the restriction enzymes selectively cut up foreign DNA. Host DNA is modified so it does not get cut up.[6] Together, these two processes are called the restriction modification system.[7] To cut the DNA, a restriction enzyme makes two cuts, once through each sugar-phosphate backbone (i.e. each strand) of the DNA double helix.


  1. Roberts RJ; Murray, Kenneth (November 1976). "Restriction endonucleases". CRC Crit. Rev. Biochem. 4 (2): 123–64. doi:10.3109/10409237609105456. PMID 795607.
  2. Kessler C, Manta V (August 1990). "Specificity of restriction endonucleases and DNA modification methyltransferases a review (Edition 3)". Gene. 92 (1–2): 1–248. doi:10.1016/0378-1119(90)90486-B. PMID 2172084.
  3. Pingoud A, Alves J, Geiger R (1993). "Chapter 8: Restriction Enzymes". In Burrell, Michael (ed.). Enzymes of Molecular Biology. Methods of Molecular Biology. Vol. 16. Totowa, NJ: Humana Press. pp. 107–200. ISBN 0-89603-234-5.{{cite book}}: CS1 maint: multiple names: authors list (link)
  4. Arber W, Linn S (1969). "DNA modification and restriction". Annu. Rev. Biochem. 38: 467–500. doi:10.1146/annurev.bi.38.070169.002343. PMID 4897066.
  5. Krüger DH, Bickle TA (September 1983). "Bacteriophage survival: multiple mechanisms for avoiding the deoxyribonucleic acid restriction systems of their hosts". Microbiol. Rev. 47 (3): 345–60. doi:10.1128/mr.47.3.345-360.1983. PMC 281580. PMID 6314109.
  6. The host DNA is methylated by a modification enzyme (a methylase) to protect it from the restriction enzyme’s activity.
  7. Kobayashi I (September 2001). "Behavior of restriction–modification systems as selfish mobile elements and their impact on genome evolution". Nucleic Acids Res. 29 (18): 3742–56. doi:10.1093/nar/29.18.3742. PMC 55917. PMID 11557807.