Final answer:
A host could theoretically have an unlimited number of prion diseases simultaneously. There are 64 possible codons which are sets of three nucleotides, and there are 20 common amino acids found in proteins. The correct option is D.
Step-by-step explanation:
The question you asked about how many species of prion can be present in a host simultaneously seems to be a trick question, as prions are not classified into species as viruses or bacteria are.
Rather, prions are misfolded proteins that can cause neurodegenerative diseases, and theoretically, a host could have multiple different prion diseases at once, although the likelihood is extremely rare. So, a more accurate answer would be D) Unlimited, within biological feasibility.
Regarding the number of possible codons, there are 64. A codon is a set of three nucleotides, and since there are four different nucleotides in mRNA (A, U, C, G), the number of possible combinations is 4 x 4 x 4, which equals 64.
The number of common amino acids found in proteins is 20. Each of these amino acids is coded for by one or more of the 64 different codons, which is an aspect of the genetic code's redundancy.