AP BIOLOGY

Detailed explanation-1: -There are 64 possible codons, three of which do not code for amino acids but indicate the end of a protein. The remaining 61 codons specify the 20 amino acids that make up proteins. The AUG codon, in addition to coding for methionine, is found at the beginning of every mRNA and indicates the start of a protein.

Detailed explanation-2: -Abstract. The universal genetic code includes 20 common amino acids. In addition, selenocysteine (Sec) and pyrrolysine (Pyl), known as the twenty first and twenty second amino acids, are encoded by UGA and UAG, respectively, which are the codons that usually function as stop signals.

Detailed explanation-3: -In genetic code, 61 codons code for 20 different types of amino acids.

Detailed explanation-4: -Because DNA consists of four different bases, and because there are three bases in a codon, and because 4 * 4 * 4 = 64, there are 64 possible patterns for a codon. Since there are only 20 possible amino acids, this means that there is some redundancy–several different codons can encode for the same amino acid.

Detailed explanation-5: -Genetic Code Each gene’s code uses the four nucleotide bases of DNA: adenine (A), cytosine (C), guanine (G) and thymine (T)-in various ways to spell out three-letter “codons” that specify which amino acid is needed at each position within a protein.