Cell Division
Cells must divide in order for an organism to grow and function properly. The process of cell division involves duplication of all the contents of the cell, including DNA, followed by the packaging of the contents into two separate cells. Most body cells undergo somatic cell division . Reproductive cell division involves the division of sperm and egg cells during the reproductive process. Somatic Cell Division: creates new somatic cells (any cell in the body other than a germ cell) to build tissues and replace dead or damaged cells. In somatic cell division, a cell undergoes nuclear division called MITOSIS.
Reproductive Cell Division: A germ cell is a gamete (sperm or oocyte) or any precursor cell destined to become a gamete. The process is called Meiosis. Discussed later.
Somatic Cell Division
A. Interphase: the cell replicates its DNA and also produces additional organelles and cytosolic components in anticipation of cell division. In Interphase the cell IS NOT dividing yet. Interphase consists of 3 phases:
G1 – Cell organelles, cytoplasm and centrosome replication begins. Cells can remain in this phase forever ( G0 – Dormant phase; cell remains in this phase until ready to divide)
S – DNA replication occurs, and the cell is COMMITTED (point of NO RETURN) to the division process. AS a result, the two daughter cells formed at the end of this process have the same genetic material.
G2 – Cell growth continues, enzymes and other proteins are synthesized. Replication of centrosomes is complete. Preparing for mitosis.
DNA Replication is the process by which the cell makes a copy if its entire genetic code. Each strand of DNA is unwound by enzyme DNA polymerase, and complementary DNA strands are synthesized from each parent strand. This process is described as semi-conservative because one-half of the original DNA strand is conserved in each new strand (an original is paired).
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