The sequence of a polypeptide is determined by the order of codons that specify the amino acids in the polypeptide. How many different sequences of codons can specify the polypeptide sequence methionine-histidine-lysine? (Use the table to fınd the number of possibilities.) SECOND BASE UCU ucc Serine (Ser) UUUL UGU UAU UAC Tyrosine (Tyr) UAA -Stop codon UAG -Stop codon Cysteine (Cys) UGA -Stop codon uGa -Tryptophan (Trp) Phenylalanine (Phe) Uuc UUAL Leucine (Leu) Uua UCA uca CU Cuc CUA FLeucine (Leu) Cu CAU CAC - Histidine (His) CCA Proline (Pro) ca CAA CAGGlutamine (Gin) cac CGA FArginine (Arg) cua AUU AUC Fisoleucine (le) AAU AAC AGU AGCSerine (Ser) Asparagine (Asn) ACA Threonine (Thr) ACG AAA AAGFLysine (Lys) AUA Methionine (Met) AUG Start codon AGGArginine (Arg) GUU) GUC QuA Valine (Val) GUG) GCU acC - Alanine (Ala) GGU GAAspartic acid (Asp) aac Giycine (Gly) GCA GAAL GGA GAG Glutamic acid (Glu) Gaa) 8 1 4 THIRD BASE FIRST BASE

You discovered a (tiny) novel protein and figured out that the protein sequence was:   Met-Ala-Arg-Gly-Trp-Ala-Pro   Work backwards (showing your work) to identify 2 possible DNA sequences that might encode your protein.            Sequence 1: ______________________________________________________________________            Sequence 2: ______________________________________________________________________     Based on these sequences, is there anything you could infer about where this organism might live? Could the DNA in your possible sequences be beneficial for any particular environments?

Adenine may also be named 6-amino purine. How would you name the other four nitrogenous bases, using this alternative system? (O is indicated by “oxy-,” and CH3 by “methyl.”)

Choose any pentapeptide composed of five different amino acids.  List the amino acids.  Present one messenger RNA codon for each amino acids and the sequence of nucleotides on the DNA that originally coded for your pentapeptide.