how do genes work?
Although each cell contains a full complement of DNA, cells use genes selectively. Some genes enable cells to make proteins needed for basic functions; dubbed housekeeping genes, they are active in many types of cells. Other genes, however, are inactive most of the time. Some genes play a role in early development of the embryo and are then shut down forever. Many genes encode proteins that are unique to a particular kind of cell and that give the cell its character – making a brain cell, say, different from a bone cell. A normal cell activates just the genes it needs at the moment and actively suppresses the rest. genes determine body processes Genes, through the proteins they encode, determine all body processes, including how the body responds to challenges from the environment.
Genes are made of four different nucleotide bases. A nucleotide is a molecule composed of a nitrogen base, a phosphate group, and a sugar. The four bases are adenine, thymine, guanine, and cytosine. Adenine (A) is always paired with thymine (T). Cytosine (C) is paired with guanine (G). Strung out together these bases form two strands in a double helix like a twisted ladder. On a chromosome genes are wound tightly, like thread over a spool. When a cell prepares to divide it unwinds the genes from their positions on the chromosome and splits the strands apart. Because adenine always bonds with thymine and guanine with cytosine the cell can remake the gene strands, copying them exactly. If one strand reads AATTCGCG then the enzymes in the cell will create a complementary strand to read TTAAGCGC. Cells draw on genetic information to produce proteins.
While each cell contains a full complement of DNA, a normal cell activates just the genes it needs at the moment and actively suppresses the rest. Some genes enable cells to make proteins needed for basic functions, some play a role in early development of the embryo and are then shut down forever, and many encode proteins that are unique to a particular kind of cell and that give the cell its character – making a brain cell, say, different from a bone cell.
