Integrated SequencePhysics Chemistry Organic Biology

Web Resources



  click if a link is broken



Special points of emphasis

Proteins

Nucleic Acids

Gene Expression

DNA Replication and Cellular Reproduction

Each eukaryotic chromosome contains a single uninterrupted molecule of DNA tightly bound to a group of small, basic proteins called histones. Chromosomes consist of approximately half DNA and protein. This composite material is called chromatin. The primary structure of histones contains many amino acids with basic side chains. Through post-translational, reversible modifications such as acetylation, methylating, ribosylation, and phosphorylation, the properties of histones may be modulated which seems to play a roll in regulating the availability of DNA for transcription and replication. Nucleosomes are the repeating units of the chromatin fiber consisting of eight histones and about 200 base pairs. The nucleosomes are themselves further packed in higher order supercoils. During the resting phase of the cell cycle, the chromosomes are predominantly unwound. As cell division approaches, the chromosomes condense, assuming flexible rod-like shapes. This permits a more orderly apportionment of genetic material among the two daughter cells.







The WikiPremed MCAT Course is a free comprehensive course in the undergraduate level general sciences. Undergraduate level physics, chemistry, organic chemistry and biology are presented by this course as a unified whole within a spiraling curriculum.

Please read our policies on privacy and shipping & returns.  Contact Us.
MCAT is a registered trademark of the Association of American Medical Colleges, which does not endorse the WikiPremed Course.


Creative Commons License
The work of WikiPremed is published under a Creative Commons Attribution Share Alike 3.0 License. There are elements of work here, such as a subset of the images in the archive from WikiPedia, that originated as GNU General Public License works, so take care to follow the unique stipulations of that license in printed reproductions. You can use the resources here for commercial or non-commercial purposes, but please give attribution and a link to the production credits and edit history of the resource. For the works here which began as my individual work, please attribute "John Wetzel, an author at wikipremed.com".