Friday, September 10, 2010
Where DNA lives
The human plastic bag that holds all the chemicals and salt water is called a cell. Trillions of them come together to keep all that water and chemicals from running out all over the place. Now imagine an egg cracked onto a skillet. You will not have to imagine because the piture to the right is just the thing. What do you notice? First there is a distinct watery looking margin that takes an oval shape. All cells in the human body have this margin called a "cell membrane". The cell membrane keeps things in and other things out. It is made up of long chains of those carbon atoms forming a water tight shield. (called a lipoprotein membrane) The most dramatic object is the large round yellow thing in the middle. This is the nucleus of the cell and it has its own special membrane called a nuclear membrane. The space between the nucles and the cell membrane is called the cytoplasm. It is here that the cell carries on its intended activites, all under the direction of the DNA housed in the yellow part (nucleus). All cells in the human body have these basic parts...a nucleus, cytoplasm, and speical membranes. It is in the cytoplasm that the special ovens called mitochrondia live. These ovens produce heat and energy that the cell needs to function. The ovens are controlled by their own special DNA called mitochrondial DNA or mtDNA. This is the DNA that has received the most attention in the press since it was first used to explore our human roots. It is the DNA that is received only through the mother, and has proved a "mother load" indeed. The nuclear DNA comes from both parents and is formed at the point of conception. If male, it is the nuclear DNA that contains the Y-chromosome that is only transmitted from the male generation to generation. So there you have it, an egg in the pan, not an egg in the face.