Where Is DNA Found?
Throughout the body - in cells...
Our bodies are formed from between 50 and 100 trillion cells (a trillion is a
thousand billion, or a thousand, thousand million). These cells are organized
into tissues, such as skin, muscle, and bone. Each cell contains all of the organism's
genetic instructions stored as DNA. However, each cell uses only the instructions
from part of the DNA. For example, a muscle cell uses the DNA that specifies
the muscle apparatus, whereas a nerve cell uses DNA that specifies the nervous
system. It is as if each cell reads only that part of a book of instructions
that it needs.
Within the cell - in chromosomes...
Each very long DNA molecule is tightly wound and packaged as a chromosome.
Humans have two sets of 23 chromosomes in every cell, one set inherited from
each parent. A human cell therefore contains 46 of these chromosomal DNA molecules.
Within each chromosome - in genes...
Each DNA molecule that forms a chromosome can be viewed as a set of shorter
DNA sequences. These are the units of DNA function, called genes, each of which
guides the production of one particular component of an organism. A set of
human chromosomes contains one copy of each of the roughly 30,000 genes in
the human "genome" - the term used to refer to the complete genetic
instructions for an organism.
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DNA is found throughout the body.
Each cell contains all of the organism's genetic instructions stored as DNA. Each very long DNA molecule is tightly wound and packaged as a chromosome. Each DNA molecule that forms a chromosome can be viewed as a set of shorter
DNA sequences. These are the units of DNA function, called genes, each of which
guides the production of one particular component of an organism. |
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