In constructing an oligonucleotide probe based on information from a protein’s sequence, one often chooses (if possible) regions of a sequence containing tryptophan or methionine residues.Why?

a. The synthesis of most proteins starts with methionineor a derivative there of, so a methionine codon assures one willstart at the beginning of the gene.

b. These two amino acids are both encoded by multiplecodons such that the degeneracy of the genetic code makes itpossible for a number of sequences to recognize and bind to thetarget sequence.

c. As these two amino acids have only one codon, the oligonucleotide probe will have a greater specificity for the DNA  fragment being sought.