Levels of Organization Image Map

Cells are very busy - sort of like a factory that is making lots of different things at the same time. As in a factory, the activities inside a cell take a lot of instructions so that the right things get done at the right time. 

Why does it matter how a cell stores information?

Experiments by Gregor Mendel, in what is now Slovakia in Eastern Europe,  revolutionized scientific thinking (see "Story Time"). But scientists in that time did not appreciate the importance of Mendel's experiments. Later scientists took a new look at Mendel's data and realized that his ideas helped to explain:

  •  Darwin's theory of evolution.

  •  the results of centuries of selective breeding of  animal and plant populations.  

with permission from The Scientist

The principles advocated by Mendel caused later scientists to look for the physical origin of traits, which we now know are found in chromosomes, which in turn contain the DNA that carries the codes for inheritable traits.

Three main fields are using the information about the code in DNA in important ways:

DNA Model ImageCRIMINAL JUSTICE. Everybody's DNA is slightly different from that of everybody else.  Thus, a sample of blood or saliva (containing tongue or cheek cells) can be used to identify a person. Police use this technique to catch criminals who leave traces of some of their cells at crime scenes. Click here for more.

MEDICINE. Doctors use DNA samples to detect the presence of inheritable diseases.  Someday soon, scientists  hope to develop "gene therapies" in which "good" genes can be inserted into cells to direct normal function.  DNA directs the production of the body's proteins, and proteins create most of the structure of cells and control most of the functions. If you have a "bad" gene, you have a bad protein.  If we can manipulate the bad gene into a good gene, we have a treatment. Or maybe, we can find ways to counteract the bad protein. Click here for more.

AGRICULTURE. Scientists can insert or delete genes inCow Image
plants or animals to improve their growth, drought toler-
ance, disease resistance, or other functions. Animals can
be cloned, so that exact copies can be made of one animal that has very desirable genetic characteristics. Click here for more.

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