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HOW MANY WORDS AND HOW MANY CODONS ARE THERE? HOW THE GENETIC CODE IS LIKE LANGUAGE
There are only 64 codons, which are like "words" in the genetic code. But there are hundreds of thousands or even millions of actual words in a widely used language. The genetic code, like language, is combinatorial. That’s why every bacterium, plant and creature is genetically different, even within the same species, and even though each uses the same 64 three-letter DNA “words.”
Here are some analogies between language and the genetic code:
Language |
Genetic Code |
|---|---|
| LETTERS 26 letters (symbols), A, B, C, etc. | NUCLEOTIDES 4 nucleotides: cytosine, guanine, adenine, and thymine |
| WORDS A word consists of one or more letters. Thousands of words are in a dictionary. Speech and written documents are comprised of words from the dictionary. | CODONS A codon consists of three adjacent nucleotides. 64 codons form the genetic dictionary. All living things use the same 64-codon dictionary. |
| SENTENCES Sequences of words are called sentences or lines of poetry, etc. They code meaningful representations of thought. | GENES Sequences of codons—strands of DNA—are called genes. They code chains of amino acid molecules called proteins, which comprise various body parts. |
| CHAPTERS Many sentences form a larger unit called a chapter. | CHROMOSOMES Many genes form a long strand of DNA called a chromosome. |
| BOOK All of the chapters containing all of the sentences form a book—perhaps 10,000 sentences. | GENOME All of the chromosomes, containing all of the genes, form the genome of the organism. Humans have 23 pairs of chromosomes, one member of each pair from each parent. The human genome consists of some 20,000 to 25,000 genes |
The fact that all life on earth is based on the same 64-codon DNA dictionary makes it a virtual certainty that all life, all microbes, plants, and animals that have ever existed—dinosaurs, oysters, apple trees, sharks, daffodils, rats, chimpanzees, and humans—evolved from the same single molecular strand, a monad (first simple organism) that fused, through natural chemical mechanisms, from non-living molecules nearly 4 billion years ago.