|Matthew S. Meselson|
24 May 1930 |
Denver, Colorado, USA
|Fields||Genetics, Molecular Biology|
|Alma mater||University of Chicago (Ph.B., 1951)
California Institute of Technology (Ph.D., 1957)
|Doctoral advisor||Linus Pauling|
|Doctoral students||Susan Lindquist|
Matthew Stanley Meselson (born May 24, 1930) is an American geneticist and molecular biologist whose research was important in showing how DNA replicates, recombines and is repaired in cells. In his mature years, he has been an active chemical and biological weapons activist and consultant. He is married to the medical anthropologist and biological weapons writer Jeanne Guillemin.
Youth and education
Meselson studied chemistry at the University of Chicago and graduated in 1951. He went on to study under Linus Pauling who assigned him work on x-ray crystallography which he later wrote a thesis on in 1958. He was a research fellow and then Assistant Professor of Physical Chemistry at Caltech until he joined the Harvard faculty in 1960, where he conducts research in molecular genetics and evolution. He started in Harvard as associate professor and taught undergraduate genetics for many years.
In 1957 with Franklin Stahl he showed that DNA replicates semi-conservatively. The Meselson-Stahl experiment used the Escherichia coli grown in the presence of the nitrogen isotope nitrogen-15, which was then switched to be grown with normal nitrogen, nitrogen-14. When they extracted the DNA using density centrifugation they found three types of DNA, one containing nitrogen-15, one containing nitrogen-14, and a hybrid containing both isotopes. When the hybrid DNA was made single stranded by heating, they could show one parental strand and one that had been newly synthesized, so when DNA is synthesized the DNA double helix splits into two, each of the single strands acting as a template for the synthesis of a complementary strand. This phenomenon is called semi-conservative DNA replication.
He showed in the years that followed many more theories in relation to this with the help of Jean Weigle. In 1961 with Sydney Brenner and François Jacob he later demonstrated that ribosomal RNA molecules are stable, which later proved the existence of mRNA - a problem scientists had struggled with previously. He later showed with Charles Radding that genetic recombination results from the splicing of DNA molecules. He also demonstrated the enzymatic basis of a process by which cells recognize and destroy foreign DNA, and discovered methyl-directed mismatch repair, which enables cells to repair mistakes in DNA.
The Meselson Effect
The "Meselson effect” is the process by which the two alleles, or copies of a gene, in an asexual diploid organism evolve independently of each other, becoming increasingly different over time. In sexual organisms the processes of recombination and independent assortment allow both of the alleles within an individual to descend from a recent single ancestral allele. Without recombination or independent assortment alleles cannot descend from a recent ancestral allele. Instead the alleles share a last common allelic ancestor at or just preceding the loss of meiotic recombination.  A striking example of this effect was described in Bdeloid rotifers where the two alleles of the lea gene have diverged into two different genes which work together to preserve the organism during periods of dehydration. Ultimately the Meselson effect would cause entire copies of an organisms’ genome to diverge from each other, effectively reducing all anciently asexual organisms to a haploid state, in a process similar to the degeneration following whole genome duplication.
However, gene conversion, a form of recombination common in asexual organisms, may prevent the Meselson effect from occurring in young asexual organisms  and may limit the effect in Bdelloid rotifers. Moreover, a number of putative examples of the Meselson effect remain controversial because other biological process, such as hybridation, can mimic the Meselson effect. Some authors have questioned whether the Meselson effect can occur in realistic populations. 
Chemical and biological weapons disarmament activism
In 1963 Meselson served as a resident consultant in the US Arms Control and Disarmament Agency, since then he has been involved in chemical and biological weapons disarmament policy formation as a consultant and through the Harvard Sussex Program, a disarmament think-tank.
- Meselson was a leader in a 1980s effort investigating allegations made by the CIA and the US State Department that "yellow rain" was a Soviet biological warfare agent. Meselson was among several scientists whose work concluded that the purported agent was bee droppings.
- In 1992–94, Meselson investigated and reported on the Sverdlovsk anthrax leak, a 1979 bio-warfare mishap in the Soviet Union that resulted in the deaths of 64 persons. Despite initially voicing support for the official Soviet story that the deaths were the unintentional result of ingestion anthrax from naturally infected cattle, Meselson was eventually forced to concede that the deaths were actually inhalation anthrax and did, in fact, come from the Sverdlovsk anthrax production plant, which existed in direct violation of the Biological Weapons Convention.
- 1975 Caltech Distinguished Alumni Award.
- 1984 MacArthur Fellows Program Genius Award.
- 1995 Genetics Society of America - Thomas Hunt Morgan Medal for lifetime contributions.
- 2002 American Society for Cell Biology’s Public Service Award for Advancing Prevention of Chemical and Biological Weapons.
- 2004 Lasker Award for Special Achievement in Medical Science. The prize honors a lifetime of solving fundamental biological problems.
- 2005 Election as Honorary Life Member to the National Academy of Sciences.
- 2008 Mendel Medal of the UK Genetics Society.
- Gitschier, J. (2011). "A Flurry of Folding Problems: An Interview with Susan Lindquist". PLoS Genetics 7 (5): e1002076. doi:10.1371/journal.pgen.1002076. PMC 3093363. PMID 21589898.
- Butlin, R. (2002). "OPINION — EVOLUTION OF SEXThe costs and benefits of sex: New insights from old asexual lineages". Nature Reviews Genetics 3 (4): 311–317. doi:10.1038/nrg749. PMID 11967555.
- Pouchkina-Stantcheva, N. N.; McGee, B. M.; Boschetti, C.; Tolleter, D.; Chakrabortee, S.; Popova, A. V.; Meersman, F.; Macherel, D.; Hincha, D. K.; Tunnacliffe, A. (2007). "Functional Divergence of Former Alleles in an Ancient Asexual Invertebrate". Science 318 (5848): 268–271. doi:10.1126/science.1144363. PMID 17932297.
- Tucker AE, Ackerman MA, Eads BD, Xu S, Lynch M. (2013) Population-genomic insights into the evolutionary origin and fate of obligately asexual Daphnia pulex. PNAS. 110:15740.
- Flot J-F, Hespeels B, Li X, Noel B, Arkhipova I, Danchin EGJ, Hejnol A, Henrissat B, Koszul R, Aury JM, Barbe V, Barthélémy RM, et al. (2013)
- Schön I, Martens K, Dijk P (2009) Lost Sex: The Evolutionary Biology of Parthenogenesis. The Netherlands: Springer. 615 p. (chapter 13)
- SCHAEFER, I., DOMES, K., HEETHOFF, M., SCHNEIDER, K., SCHÖN, I., NORTON, R. A., SCHEU, S. and MARAUN, M. (2006), No evidence for the ‘Meselson effect’ in parthenogenetic oribatid mites (Oribatida, Acari). Journal of Evolutionary Biology, 19: 184–193. doi: 10.1111/j.1420-9101.2005.00975.x
- David B. Mark Welch, Jessica L. Mark Welch and Matthew Meselson. Evidence for degenerate tetraploidy in bdelloid rotifers PNAS 2008 105 (13) 5145-5149; published ahead of print March 24, 2008, doi:10.1073/pnas.0800972105
- Jae H. Hur,Karine Van Doninck,Morgan L. Mandigo and Matthew Meselson. Degenerate Tetraploidy Was Established Before Bdelloid Rotifer Families Diverged Mol Biol Evol (2009) 26 (2): 375-383 first published online November 7, 2008 doi:10.1093/molbev/msn260
- Stoeckel S, Masson J-P (2014) The Exact Distributions of FIS under Partial Asexuality in Small Finite Populations with Mutation. PLoS ONE 9(1): e85228. doi: 10.1371/journal.pone.0085228
- Yellow rain: Thai bees' faeces found doi:10.1038/308485b0 PMID 6709055
- Yellow rain evidence slowly whittled away doi:10.1126/science.3715471 PMID 3715471
- Matthew Meselson
- Matthew Meselson's short talk: The Semi-Conservative Replication of DNA
- Matthew Meselson's bio at Harvard Kennedy School
- The Meselson Laboratory
- The Meselson - Stahl Experiment
- Video of a talk by Meselson titled "Linus Pauling as an Educator"