Question

10. You have partially sequenced the protein from a kangaroo. The sequence is Leu Met Asp Cys Trp Ile Thr Phe Ile. You want to extract the corresponding gene from wombats which you believe has the same amino acid sequence as shown. To identify the gene you want to synthesise an oligonucleotide of 15 bases for use as a probe. What region of the peptide would you use to develop your oligo using the least number of combinations but giving a sequence that must be absolutely complementary to your corresponding wombat sequence?

Answer 1

The probe oligonucleotide has only 15 bases. Which means the region of peptide that could be used would contain 5 amino acids because an amino acid is coded by 3 bases known as a codon. But some amino acids are coded by more than one codon. To make the oligonucleotide most specific, amino acids with least codons should be selected. Since methionine(Met) and tryptophan(Trp) have only one codon each, part of the peptide that has these amino acids is to be selected. Hence the portion of peptide to be used is Leu Met Asp Cys Trp.