GENETIC DISORDERS

1. Intro

As scientists are discovering more about human DNA they find hundreds of variations and deviations. Considering the difficulties involved--the 6 feet of DNA in a human cell consists of 6 billion subunits, or base pairs, coiled and tightly packed into 46 chromosomes, all of which must be duplicated every time a cell divides--our general state of health is something of a miracle.

We each inherit hundreds of genetic mutations from our parents. In addition, the DNA in our own cells undergoes an estimated 30 new mutations during our lifetime, either through mistakes during DNA copying or cell division or, more often, because of damage from the environment.

Imagine a corrupted file or fragmented hard drive if you use a computer and you get the picture!

Some bits of our DNA may be deleted, inserted, broken, or substituted. Most mutations affect only the parts of DNA that do not contain instructions for making a gene, so we don’t worry about them.

If there is an error in DNA that alters a message that tells certain cells to manufacture a certain protein, then there is a problem.

To stay alive and functioning, the human body requires billions of fresh protein molecules daily--about 50,000 different kinds of proteins that must be supplied in the right quantities, at the right times, and in the right places.

We need hemoglobin to carry oxygen through the bloodstream, antibodies to fight foreign substances, hormones to deal with stress, neurotransmitters to evoke movements, emotions, and thought, and many other proteins to give structure to organs or speed up chemical reactions.

Abnormal numbers of chromosomes are very often incompatible with life. In general, the human body can tolerate extra genetic material more easily than it can tolerate missing genetic material. Much of the recent progress in reading DNA has come from analyses of genetic errors (Howard Hughes Medical Institute).

The range of human variation is so great that often differences are not considered "disorders" by the medical profession. Some differences have been given the label of disorder because of the impact on the individual who has the genetic difference.

(next section - 2. Single Gene Disorders)