increases prior to mitosis, combines with the cyclin-
dependent protein kinase, and forms an active MPF
complex. The MPF phosphorylates lamin, a structural
protein of the nuclear envelope that assists in maintain-
ing the nuclear shape, among other substrates, causing
the dissolution of the nuclear envelope, which triggers
the initial phases of mitosis. Formerly called matura-
tion-promoting factor.
M phase Mitosis in eukaryote cells; when a cell
divides into two daughter cells, each with the identical
chromosomes as the parent cell.
Muller, Hermann Joseph (1890–1967) American
Geneticist Hermann Joseph Muller was born in New
York City on December 1, 1890. He attended public
school in Harlem and later Morris High School in the
Bronx.He attended Columbia University in 1907.
He obtained a teaching assistantship in zoology at
Columbia (1912–15) and received a Ph.D. in 1916.
After three years at the Rice Institute, Houston, Texas,
and at Columbia as an instructor, in 1920 Muller
became an associate professor (later professor) at the
University of Texas, Austin, where he remained until
- In 1932 he was awarded a Guggenheim Fellow-
ship and for a year worked at Oscar Vogt’s institute in
Berlin and then spent three and a half years as senior
geneticist at the Institute of Genetics of the Academy of
Sciences of the USSR, first in Leningrad and later
(1934–37) in Moscow. He moved to the Institute of
Animal Genetics, University of Edinburgh (1937–40),
and he did both teaching and research at Amherst Col-
lege as a professor from 1942 to 1945. At Amherst he
completed a large-scale experiment showing the rela-
tionship of aging to spontaneous mutations. In 1945 he
accepted a professorship in the zoology department at
Indiana University, Bloomington, Indiana, and retired
in 1964.
His method for recognizing spontaneous gene
mutation led to his discovery of a technique for artifi-
cially inducing mutations using X rays, showing in
1927 that mutations could be induced by radiation.
For this discovery, he was awarded the 1946 Nobel
Prize in physiology or medicine.
Muller contributed over 300 articles on biological
subjects to scientific publications. His principal books
are The Mechanism of Mendelian Hereditywith T. H.
Morgan, 1915; Out of the Night—a Biologist’s View
ofthe Future,1935, 1936, and 1938; and Genetics,
Medicine and Manwith C. C. Little and L. H. Snyder,- He also wrote articles on the biological effects
of atomic radiation. He was awarded numerous hon-
orary degrees and other recognitions. During the
1930s and 1940s, his controversial views on eugenics
and unpopular opinions about the hazards of radiation
forced him to leave the United States and to work in
Russia, but he came back. During the late 1940s his
criticisms on nuclear fallout were recognized by his
peers.
He was known as the father of radiation genetics
and died on April 5, 1967, in Indianapolis.
Müller, Paul Hermann(1899–1965) SwissChemist
Paul Hermann Müller was born in Olten, Solothurn,
Switzerland, on January 12, 1899. He attended prima-
ry school and the Free Evangelical elementary and sec-
ondary schools. He began working in 1916 as a
laboratory assistant at Dreyfus and Company, followed
by a position as an assistant chemist in the Scientific-
Industrial Laboratory of their electrical plant. He
attended Basel University and received a Ph.D. in 1925.
He became deputy director of scientific research on
substances for plant protection in 1946.
Müller began his career with investigations of dyes
and tanning agents with the J. R. Geigy Company,
Basel (1925–65), and beginning in 1935 concentrated
his research to find an “ideal” insecticide, one that had
rapid, potent toxicity for the greatest number of insect
species, while causing little or no damage to plants and
warm-blooded animals. He tested and concluded that
dichlorodiphenyltrichloroethane (DDT) was the ideal
insecticide.
In 1939 DDT was successfully tested against the
Colorado potato beetle by the Swiss government and
then by the U.S. Department of Agriculture in 1943.
For this discovery of DDT’s potent toxic effects on
insects Müller received the Nobel Prize in physiology
or medicine. DDT proved to be a two-edged sword.
With its chemical derivatives, DDT became the most
widely used insecticide for more than 20 years and was
a major factor in increased world food production and
suppression of insect-borne diseases, but the
widespread use of the chemical made it hazardous toMüller, Paul Hermann 231