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Home Test Kits :: What
is DNA
What Is DNA
DNA is the genetic material within every cell in the body that determines the inheritance of eye color,
hair color, stature, bone density and many other human characteristics.
DNA is a very long but narrow string-like object. A one
foot long string or strand of DNA is normally packed into a space roughly equal to a cube 1/millionth of an
inch on a side, this is possible only because DNA is a very thin string.
Our body's cells each contain a complete sample of our DNA. One cell is roughly equal in size to the cube
described in the previous paragraph. There are muscle cells, brain cells, liver cells, blood cells, sperm
cells and others. Basically, every part of the body is made up of these tiny cells and each contains a
sample or complement of DNA identical to that of every other cell within a given person. There are a few
exceptions. For example, our red blood cells lack DNA. Blood itself can be typed because of the DNA
contained in our white blood cells.
Not only does the human body rely on DNA but so do most living things including plants, animals and
bacteria.
A strand of DNA is made up of tiny building blocks. There are only four, different basic building blocks.
Scientists usually refer to these using four letters for the four different building blocks. The letters
are: A, T, G, and C. These four letters are short nicknames for more complicated chemical names, but
actually the letters (A,T, G and C) are used much more commonly than the chemical names so the latter will
not be mentioned here. Another way of referring to the building blocks or letters is to call them bases.
For example, to refer to a particular piece of DNA, we might write: AATTGCCTTTTAAAAA. This is a perfectly
acceptable way of describing a piece of DNA. Someone with a machine called a DNA synthesizer could actually
synthesize the same piece of DNA from the information AATTGCCTTTTAAAAA alone.
The sequence of bases (letters) can code for many properties of the body's cells. The cells can read this
code. Some DNA sequences encode important information for the cell. Such DNA is called, not surprisingly,
"coding DNA." Our cells also contain much DNA that doesn't encode anything that we know about. If the DNA
doesn't encode anything, it is called non-coding DNA or sometimes, "junk DNA."
The DNA code, or genetic code as it is called, is passed through the sperm and egg to the offspring. A
single sperm cell contains about three billion bases consisting of A, T, G and C that follow each other in
a well-defined sequence along the strand of DNA.
Both coding and non-coding DNA's may vary from one individual to another. These DNA variations can be used
to identify people or at least distinguish one person from another. |