General ---------Biology----------------------------------------------------- ------------------Online---------------------------------------bwilcox@edison.edu Ch. 17 From Gene to Protein

How do genes carried on the DNA molecule produce traits in the organism?

Answer:  Genes produce proteins.  Proteins catalyze reactions in chemical pathways.  These chemical reactions produce products such as pigments, other proteins, organelles, cells, hormones.  Fig. 17.2 gives an overview of the steps involved.

Examples:
Sickle cell :   the gene codes for a particular protein, hemoglobin, that is produced by a ribosome.  The Sickle-cell disease is the result of a mutation in the gene, and the hemoglobin produced is a poor oxygen carrier that causes red blood cells to be misshapen. 

Some traits, such as complex behavior, are the result of several genes producing several different proteins.  These proteins interact in chemical pathways to produce other proteins,  hormones and other chemicals that effect certain portions of the brain.  The brain creates emotions, and emotion drives our bodies to act, i.e. to exhibit certain behaviors.  The emotion may be a simple pain response to intense stimulation of a heat receptor, causing us to jerk our finger away from the hot stove and remember not to touch it again.  Or, the emotion may be a complex feeling of love that is so powerful that it can override our will to survive, and we risk our life to save a child.

Remember the two identical twins in "The Geometry of Life" video who were separated at birth, yet both became firemen?  The psychologist who did these studies concluded, with surprise, that there seems to be "a pervasive genetic influence" in behavior.  There is also an environmental influence in both complex behavior and in simple traits such as flower color or nearsitedness (myopia).  The pH of the soil can influence certain pigments to vary in color.  To need glasses to see at a distance later in life requires a certain gene and close visual work such as reading or drawing.

Understanding behavior, curing many diseases and geneitically engineering more nutritious plant species all require a detailed understanding of how genes make proteins.  As you explore this Chapter 17, "From Gene to Protein," keep in mind these broader implications.  This will not only make your study more interesting, it will help you create your "knowledge tree" and help you remember what you learn and apply it to solve problems.