Chromosome, Prokaryotic - Research Article from Macmillan Science Library: Genetics

This encyclopedia article consists of approximately 5 pages of information about Chromosome, Prokaryotic.
This section contains 1,431 words
(approx. 5 pages at 300 words per page)
Buy the Chromosome, Prokaryotic Encyclopedia Article

Chromosome, Prokaryotic

The E. Coli Chromosome Is a Single Circle.

Because the single DNA molecule forming the chromosome is so long (about 4.6 million base pairs), it is easily broken when researchers try to isolate it. However, in the early 1960s, the Australian biochemist John Cairns was able to gently lyse E. coli cells without breaking the chromosome. He was interested in chromosomal replication and had labeled the DNA with tritium (3H), a radioactive form of hydrogen. Autoradiograms of the DNA demonstrated that the bacterial chromosome is a circular molecule. While the vast majority of bacterial species possess a single unique chromosome, there are a few rare species, such as Vibrio cholerae (the agent that causes the disease cholera) and Deinococcus radiodurans, that have two different chromosomes.

Figure 1. The circular genetic map of the Escherichia coli chromosome. The map is divided into 100 map units, and representative genes are shown. The lac operon is at approximately 8 minutes. The origin of replication (not shown) is at 83.5 minutes. Based on Ingraham, 2000. Figure 1. The circular genetic map of the Escherichia coli chromosome. The map is divided into 100 map units, and representative genes are shown...

(read more)

This section contains 1,431 words
(approx. 5 pages at 300 words per page)
Buy the Chromosome, Prokaryotic Encyclopedia Article
Copyrights
Macmillan Science Library: Genetics
Chromosome, Prokaryotic from Macmillan Science Library: Genetics. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.