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DNA’s twisting, ladder-like shape stores and transmits the code that describes how to build and maintain an organism’s body.
Writing this code requires four chemical compounds or “bases” of adenine (A), thymine (T), guanine (G), and cystosine (C). Changing the sequence of these bases spells out the words and sentences that create different kinds of organisms.
The DNA Alphabet
If you “read” along a strand of DNA, you’ll see that the four chemical compounds of A,T,G, and C group together to form “words,” such as GTG ACC TCG, etc. While these words may seem like gibberish to us, they have specific meaning to a cell. We call these groups of words, or sentences, “genes.”
Genes can be strung together to create incredibly long segments or descriptions. So, just as the letters in an alphabet combine to form words and sentences, the genes spell out the set of instructions that a cell follows to do its job.
The Job of Genes
If you were to look at a genetic “sentence,” you’d see that it begins and ends with a code that tells a gene when to activate and when to shut down. Sandwiched in the middle is coding that describes the gene’s job. Together, these codes regulate cell function during different parts of an organism’s development.
In general, genes determine an organism’s traits—how it looks and functions. Traits can be visible, like freckles, flower color, or fur patterns. But some traits are hard to see, like the risk of getting cancer.
To pass on a copy of these genes to offspring, DNA must replicate itself.
Continue to How Is DNA Passed On? >>
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