DNA and the Developing Embryo
Inside almost every cell in every living organism
is a long, twisted, ladder-like molecule known as DNA. The information
contained in the DNA molecule provides a "blueprint," or a set
of codes, for building other molecules used by the cell.
As the organism grows, different parts of the
DNA molecule, called genes, are decoded and read by the cells.
Each gene contains instructions for building a particular molecule
that's needed by the growing body.
As the organism develops, different genes in
different cells may be read. The ultimate fate of any one cell--whether
it becomes a skin cell, a nerve cell, a kidney cell, or a bone
cell--depends upon which genes are read. If any of the genes are
missing, if they are misread, read out of sequence, or altered
in any way, the cell or organism may dramatically change.
The timing of this process depends on the embryo's
stage of development and the location of the cell. Developing
eye cells, for instance, use different combinations of genes than
do brain cells or skin cells. The embryos here are all in the
same stage of development. Their physical similarities and differences
correspond to variations in their genes.
|
