Most amino acids are coded for by a set of similar codons (see figure 17.6). propose at least one
evolutionary explanation to account for this pattern

The number of nucleotides that are present on DNA is the cause of this "degeneration" of the genetic code.

Explanation:

There are 20 different aminoacids that can be used to synthesize proteins. If only one nucleotide encoded each aminoacid, we would only have 4 different aminoacids, because there are only four types of nucleotides on our DNA; adenine, thymine, guanine and cytosine.

If two nucleotides encoded each aminoacid, we would be able to have different aminoacids. Still not enough.

If three nucleotides encode each aminoacid, we have different aminoacids. These exceeds the number of aminoacids available for protein synthesis, so more than one codon (set of 3 nucleotides) encode for the same aminoacid.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).

population. population is the number of people or animals in a particular place. an example of population is over eight million people living in new york city.

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