Coding exercise on Python dictionaries. Look at the DNA translation code (with the included dictionary for the codons to amino acids), STANDARD_GENETIC_CODE = { 'UUU':'Phe', 'UUC':'Phe', 'UCU':'Ser', 'UCC':'Ser', 'UAU':'Tyr', 'UAC':'Tyr', 'UGU':'Cys', 'UGC':'Cys', 'UUA':'Leu', 'UCA':'Ser', 'UAA':None, 'UGA':None, 'UUG':'Leu', 'UCG':'Ser', 'UAG':None, 'UGG':'Trp', 'CUU':'Leu', 'CUC':'Leu', 'CCU':'Pro', 'CCC':'Pro', 'CAU':'His', 'CAC':'His', 'CGU':'Arg', 'CGC':'Arg', 'CUA':'Leu', 'CUG':'Leu', 'CCA':'Pro', 'CCG':'Pro', 'CAA':'Gln', 'CAG':'Gln', 'CGA':'Arg', 'CGG':'Arg', 'AUU':'Ile', 'AUC':'Ile', 'ACU':'Thr', 'ACC':'Thr', 'AAU':'Asn', 'AAC':'Asn', 'AGU':'Ser', 'AGC':'Ser', 'AUA':'Ile', 'ACA':'Thr', 'AAA':'Lys', 'AGA':'Arg', 'AUG':'Met', 'ACG':'Thr', 'AAG':'Lys', 'AGG':'Arg', 'GUU':'Val', 'GUC':'Val', 'GCU':'Ala', 'GCC':'Ala', 'GAU':'Asp', 'GAC':'Asp', 'GGU':'Gly', 'GGC':'Gly', 'GUA':'Val', 'GUG':'Val', 'GCA':'Ala', 'GCG':'Ala', 'GAA':'Glu', 'GAG':'Glu', 'GGA':'Gly', 'GGG':'Gly'}
def proteinTranslation(seq, geneticCode): """ This function translates a nucleic acid sequence into a protein sequence, until the end or until it comes across a stop codon """ seq = seq. replace('T','U') # Make sure we have RNA sequence proteinSeq = [] i = 0 while i+2 < len(seq): codon = seq[i:i+3] aminoAcid = geneticCode[codon] if aminoAcid is None: # Found stop codon break proteinSeq. append(aminoAcid) i += 3
Give a short verbal description of what the code does on each line. Then start typing the code out on the online Python interpreter, but use an alternative dictionary with key-values for codons to amino acid called NON_STANDARD_GENETIC_CODE. Just type the first 20 key-value pairs or so from the STANDARD_GENETIC_CODE dictionary shown in the book. Now what you need to do for this exercise is to modify the "def proteintranslation" function, so that it has an "if"statement before the line where it pulls the codons from the dictionary. With this modification, our code will first check if that codon exists in the dictionary, and if not it sets the codon to a default codon='X', else it sets the default codon = seq[i:i+3]. You need to have the code working by writing out the def function, and demonstrating that you can call the function with a DNA sequence, and print out the translation of the DNA string. Try it with a few different DNA strings, and see how many X's you get.

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a  social news website  is an  internet  website  that features  user-posted stories. such stories are ranked based on popularity, as voted on by other users of the site or by website administrators. users typically comment online on the news posts and these comments may also be ranked in popularity. since their emergence with the birth of  web 2.0, social news sites have been used to link many types of information, including news, humor, support, and discussion. all such websites allow the users to submit content and each site differs in how the content is moderated. on the  slashdot  and  fark  websites,  administrators  decide which articles are selected for the front page. on  reddit  and  digg, the articles that get the most votes from the community of users will make it to the front page. many social news websites also feature an online comment system, where users discuss the issues raised in an article. some of these sites have also applied their voting system to the comments, so that the most popular comments are displayed first. some social news websites also have a  social networking  function, in that users can set up a user profile and follow other users' online activity on the website.