DNA, RNA, Chromosomes, and Genes


What is the genetic code?

The genetic code is a chart depicting the relationship between each of the possible mRNA codons and their associated amino acids. The codons are grouped according to the amino acid they code for. Present in the code as well are the “start” and “stop” codons. The start codon actually codes for methionine, which is always the first amino acid in the polypep-tide sequence. (Methionine may appear elsewhere in the polypeptide as well.) A stop codon signals the end of coding. Instead of a tRNA, with its amino acid in tow, a release factor matches the stop codon during translation, causing the polypeptide to be released from the ribosome. It is interesting to note that the genetic code contains only one start codon— AUG (and also codes for methionine)—but three stop codons—UAA, UGA, and UAG.


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