Matthew Meselson
Encyclopedia
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
.
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.
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 synthesised, so when DNA is synthesised 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 Frank Stahl, 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.
in bdelloid rotifers. Meselson described the "Meselson effect", in which two alleles in an asexual organism evolve independently and divergently over time, producing what is essentially two genomes in one organism. This is due to the lack of sexual recombination which would have shuffled alleles between chromosomes during meiosis
. Meselson's laboratory provided exciting evidence that this is indeed the case in asexual bdelloid rotifers, and the Meselson effect was subsequently used to explain how bdelloid rotifers deal with dehydration. Dr. Alan Tunnacliffe's Cambridge lab showed that the lea gene
had diverged through the Meselson effect into two different genes whose protein
products work in synergy
to preserve the organism during periods of dehydration
, suggesting that the Meselson effect is a mechanism of generating variation
that confers evolutionary advantage
.
, 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.
Geneticist
A geneticist is a biologist who studies genetics, the science of genes, heredity, and variation of organisms. A geneticist can be employed as a researcher or lecturer. Some geneticists perform experiments and analyze data to interpret the inheritance of skills. A geneticist is also a Consultant or...
and molecular biologist whose research was important in showing how DNA replicates
DNA replication
DNA replication is a biological process that occurs in all living organisms and copies their DNA; it is the basis for biological inheritance. The process starts with one double-stranded DNA molecule and produces two identical copies of the molecule...
, recombines
Genetic recombination
Genetic recombination is a process by which a molecule of nucleic acid is broken and then joined to a different one. Recombination can occur between similar molecules of DNA, as in homologous recombination, or dissimilar molecules, as in non-homologous end joining. Recombination is a common method...
and is repaired
DNA repair
DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as UV light and radiation can cause DNA damage, resulting in as many as 1...
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
Jeanne Guillemin
Jeanne Harley Guillemin is a medical anthropologist, who for twenty-five years was a Professor of Sociology at Boston College and for the last ten years, a senior fellow in the Security Studies Program at Massachusetts Institute of Technology...
.
Youth and education
Meselson studied chemistry at the University of ChicagoUniversity of Chicago
The University of Chicago is a private research university in Chicago, Illinois, USA. It was founded by the American Baptist Education Society with a donation from oil magnate and philanthropist John D. Rockefeller and incorporated in 1890...
and graduated in 1951. He went on to study under Linus Pauling
Linus Pauling
Linus Carl Pauling was an American chemist, biochemist, peace activist, author, and educator. He was one of the most influential chemists in history and ranks among the most important scientists of the 20th century...
who assigned him work on x-ray crystallography
X-ray crystallography
X-ray crystallography is a method of determining the arrangement of atoms within a crystal, in which a beam of X-rays strikes a crystal and causes the beam of light to spread into many specific directions. From the angles and intensities of these diffracted beams, a crystallographer can produce a...
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
Harvard University
Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...
as associate professor and taught undergraduate genetics
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
for many years.
DNA breakthroughs
In 1957 with Franklin StahlFranklin Stahl
Dr. Franklin William Stahl is an American molecular biologist. With Matthew Meselson, Stahl conducted the famous Meselson-Stahl experiment showing that DNA is replicated by a semiconservative mechanism, meaning that each strand of the DNA serves as a template for the "replicated" strand.He is...
he showed that DNA replicates semi-conservatively. The Meselson-Stahl experiment
Meselson-Stahl experiment
The Meselson–Stahl experiment was an experiment by Matthew Meselson and Franklin Stahl in 1958 which supported the hypothesis that DNA replication was semiconservative. Semiconservative replication means that when the double stranded DNA helix was replicated, each of the two double stranded DNA...
used the Escherichia coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
grown in the presence of the nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
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 synthesised, so when DNA is synthesised 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
Jean Weigle
Jean-Jacques Weigle was a Swiss molecular biologist at the CalTech and a former physicist at the University of Geneva from 1931 to 1948. He is known for his major contributions on field of the bacteriophage λ research, focused on the interactions between those viruses and their E...
. In 1961 with Frank Stahl, Sydney Brenner
Sydney Brenner
Sydney Brenner, CH FRS is a South African biologist and a 2002 Nobel prize in Physiology or Medicine laureate, shared with H...
and François Jacob
François Jacob
François Jacob is a French biologist who, together with Jacques Monod, originated the idea that control of enzyme levels in all cells occurs through feedback on transcription. He shared the 1965 Nobel Prize in Medicine with Jacques Monod and André Lwoff.-Childhood and education:François Jacob is...
he later demonstrated that ribosomal RNA
Ribosomal RNA
Ribosomal ribonucleic acid is the RNA component of the ribosome, the enzyme that is the site of protein synthesis in all living cells. Ribosomal RNA provides a mechanism for decoding mRNA into amino acids and interacts with tRNAs during translation by providing peptidyl transferase activity...
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
Genetic recombination
Genetic recombination is a process by which a molecule of nucleic acid is broken and then joined to a different one. Recombination can occur between similar molecules of DNA, as in homologous recombination, or dissimilar molecules, as in non-homologous end joining. Recombination is a common method...
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 laboratory studies the evolution of asexualityAsexual reproduction
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...
in bdelloid rotifers. Meselson described the "Meselson effect", in which two alleles in an asexual organism evolve independently and divergently over time, producing what is essentially two genomes in one organism. This is due to the lack of sexual recombination which would have shuffled alleles between chromosomes during meiosis
Meiosis
Meiosis is a special type of cell division necessary for sexual reproduction. The cells produced by meiosis are gametes or spores. The animals' gametes are called sperm and egg cells....
. Meselson's laboratory provided exciting evidence that this is indeed the case in asexual bdelloid rotifers, and the Meselson effect was subsequently used to explain how bdelloid rotifers deal with dehydration. Dr. Alan Tunnacliffe's Cambridge lab showed that the lea gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
had diverged through the Meselson effect into two different genes whose protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
products work in synergy
Synergy
Synergy may be defined as two or more things functioning together to produce a result not independently obtainable.The term synergy comes from the Greek word from , , meaning "working together".-Definitions and usages:...
to preserve the organism during periods of dehydration
Dehydration
In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
, suggesting that the Meselson effect is a mechanism of generating variation
Genetic diversity
Genetic diversity, the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary....
that confers evolutionary advantage
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
.
Chemical and biological weapons disarmament activism
In 1963 Meselson served as a resident consultant in the US Arms Control and Disarmament AgencyArms Control and Disarmament Agency
The U.S. Arms Control and Disarmament Agency was established as an independent agency of the United States government by the Arms Control and Disarmament Act , September 26, 1961, a bill drafted by presidential adviser John J. McCloy. Its predecessor was the U.S. Disarmament Administration, part...
, since then he has been involved in chemical and biological weapons disarmament
Disarmament
Disarmament is the act of reducing, limiting, or abolishing weapons. Disarmament generally refers to a country's military or specific type of weaponry. Disarmament is often taken to mean total elimination of weapons of mass destruction, such as nuclear arms...
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 rainYellow rainYellow rain was a political incident in which the United States Secretary of State Alexander Haig accused the Soviet Union of supplying T-2 mycotoxin to the Communist states in Vietnam and Laos for use in counterinsurgency warfare....
" 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 leakSverdlovsk anthrax leakThe Sverdlovsk anthrax leak is an incident when spores of anthrax were accidentally released from a military facility in the city of Sverdlovsk 1450 km east of Moscow on April 2, 1979. This accident is sometimes called "biological Chernobyl"...
, a 1979 bio-warfare mishap in the Soviet UnionSoviet UnionThe Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
that resulted in the deaths of 64 persons. Despite his earlier efforts to demonstrate the "innocent" nature of the accident, Meselson's investigation incontrovertably proved that the Soviets had a secret bio-weapons program in violation of the Biological Weapons ConventionBiological Weapons ConventionThe Convention on the Prohibition of the Development, Production and Stockpiling of Bacteriological and Toxin Weapons and on their Destruction was the first multilateral disarmament treaty banning the...
.
Selected Awards
- 1975 Caltech Distinguished Alumni Award.
- 1984 MacArthur Fellows ProgramMacArthur Fellows ProgramThe MacArthur Fellows Program or MacArthur Fellowship is an award given by the John D. and Catherine T...
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.