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From cell to gene
Your genome is located right in the heart of the cells,
in the nucleus.
Every one of your body's trillions of cells truly belongs to you.
With a few exceptions, each one of them contains a complete copy
of your genome.
Your genome is composed of 3.4 billion chemical letters, called
bases.
These letters follow one another in an order that is specific and
unique to form your DNA.
This DNA is a complex molecule that looks like a long ladder twisted
into a double helix shape.
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What are genes?
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 Father,
daughters and mother.
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The genes,
parts of the DNA, are the functional units of the genome. They hold
all the information necessary to create the proteins
you need. You have between 20 000 and 25 000 genes, which carry information
to make proteins that determine many of your traits. Traits are
characteristics that are passed on to you from your parents, including
things like your hair colour and ear shape. We inherit half our
genes from our father and half from our mother.
Genes are located along thread-like structures called chromosomes.
Chromosomes are found in the nucleus of the cell, and consist of
DNA and proteins. One chromosome may contain thousands of genes.
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Image:
K.G. Murti, Visuals Unlimited, Inc.
Human chromosomes. |
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In most animal cells, chromosomes come in pairs, referred to as
diploid. But there are many possibilities. For example, some plants
are tetraploid (where chromosomes come in fours) and some are octaploid
(where chromosomes come in eights!).
In humans, a cell nucleus contains 23 pairs of chromosomes. For
males, 22 of these pairs are of matching chromosomes, and the 23rd
pair contains the different X and Y, or sex chromosomes. Females
have two X chromosomes in their 23rd pair.
Other living things have different numbers of chromosomes. For
example, a fruit fly cell only has 4 pairs of chromosomes, a horse's
cell has 32 pairs, and your dog's cells have 39 pairs! |
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How do genes work?
Genes carry instructions for making proteins in cells. Proteins
are an important part of the many biological processes that
take place in the cells in your body.
Although each cell contains a full set of DNA, individual
cells use genes selectively.
Some genes are used for common internal functions within
many types of cells. Some genes are involved in embryonic
development, and then are never used again. Some genes help
define the character of specific cells, differentiating a
brain cell from a liver cell, for example. Other genes may
be inactive most of the time.
"A normal cell activates just the genes it needs at
the moment and actively suppresses the rest."
[Source: Access
Excellence Resource Center]
How does the information contained in genes get turned into
proteins? See protein synthesis
to find out more.
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You must have QuickTime or Windows Media Player in order to see the videos. You
can download QuickTime
from the Apple Web site, or download
Windows Media Player from the Microsoft Web site. |
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