Barbara McClintock

For the illustrator named Barbara McClintock see Barbara McClintock (illustrator).

University of Missouri - Columbia

During her time at Missouri, McClintock expanded her research on the effect of X-rays on maize cytogenetics. McClintock observed the breakage and fusion of chromosomes in irradiated maize cells. She also could show that, in some plants, spontaneous chromosome breakage occurred in the cells of the endosperm. Following the course of mitosis she observed that the ends of broken chromatids were rejoined after the chromosome replication. In the anaphase of mitosis, the broken chromosomes formed a chromatid bridge, which was broken when the chromatids moved towards the cell poles. The broken ends were rejoined in the interphase of the next mitosis, and the cycle was repeated causing massive mutation which she could detects as variegation in the endosperm. This cycle of breakage, fusion, and bridge also described as the breakage?rejoining?bridge cycle was a key cytogenetic discovery for several reasons. First it showed that the rejoining of chromosomes was not a random event, and secondly it demonstrated a source of large scale mutation and it remains an area of interest in cancer research today for this reason.

Related Topics:
Mitosis - Replication - Anaphase - Interphase - Cancer

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Although her research was progressing at Missouri McClintock was not satisfied with her position at the University. She was excluded from faculty meeting as was not made aware of positions available at other institutions. In 1940 she wrote to Charles Burnham, "I have decided that I must look for another job. As far as I can make out, there is nothing more for me here. I am an assistant professor at $3,000 and I feel sure that that is the limit for me." {{ref|1940letter}} She was also aware that her position had been especially created for her by Stadler and may depend on his presence. McClintock believed she would not gain tenure at Missouri and in 1941, she took a leave of absence to visit Columbia University where her Cornell colleague Marcus Rhoades was a professor. He offered to share his research field at Cold Spring Harbor on Long Island. In December 1941 she was offered a research position by Milislav Demerec and she joined the staff of the Carnegie Institution of Washington's Department of Genetics Cold Spring Harbor Laboratory.

Related Topics:
Tenure - Columbia University - Milislav Demerec - Carnegie Institution of Washington - Cold Spring Harbor Laboratory

~ ~ ~ ~ ~ ~ ~ ~ ~ ~