AP BIOLOGY

Detailed explanation-1: -A codon is a DNA or RNA sequence of three nucleotides (a trinucleotide) that forms a unit of genomic information encoding a particular amino acid or signaling the termination of protein synthesis (stop signals). There are 64 different codons: 61 specify amino acids and 3 are used as stop signals.

Detailed explanation-2: -The three-letter nature of codons means that the four nucleotides found in mRNA-A, U, G, and C-can produce a total of 64 different combinations.

Detailed explanation-3: -Three codons, UAA, UAG, and UGA, are known as stop codons as they stop the process of translation. If this is a mutation as a stop codon and its finishes prematurely it is called an amber codon. AUG is also known as a start codon, as it initiates the process of translation.

Detailed explanation-4: -Multiple codons can code for the same amino acid. The codons are written 5’ to 3’, as they appear in the mRNA. AUG is an initiation codon; UAA, UAG, and UGA are termination (stop) codons.

Detailed explanation-5: -Answer and Explanation: Codons must consist of three nucleotides because this gives the cell the appropriate amount of combinations to code for all twenty amino acids with some redundancy. There are four possible bases in DNA. So, if each codon was only one nucleotide, we could only code for four amino acids.