Troque Week 2
Contents
The Genetic Code
In order to obtain the complementary strand of DNA from the original, each of the four bases, A, T, C, and G, should be transcribed into their counterpart bases (i.e. the only bases they connect to in a DNA strand). Therefore, the A in the original strand should be paired with T in the complementary; T, C, and G from the original should be paired with A, G, and C respectively. Additionally, since the original is in the 5' to 3' direction, the complementary strand should be written in the 3' to 5' direction since we are writing the complementary bases directly beneath the original strand and it would make the most sense to do it this way.
- Below is the strand of DNA and its complementary
Original: 5’-cgtatgctaataccatgttccgcgtataacccagccgccagttccgctggcggcatttta-3’ Complementary: 3'-gcatacgattatggtacaaggcgcatattgggtcggcggtcaaggcgaccgccgtaaaat-5'
From the original strand, turn all the T's into U's in order to get the mRNA strand. This strand will be the +1 reading frame since we are reading the strand from the very first 3 bases (codons). For +2 and +3 reading frames, we shift our first codon so that we do not include the very first base. This means that we translate a codon starting from bases 2, 3, and 4 instead of 1,2, and 3 for +2; similarly, for +3 reading frame, we start translating into proteins from bases 3, 4, and 5. In order to translate the mRNA strand into its respective amino acid sequence, we look at a codon table which shows what each codon corresponds to which amino acid. Since the 3 consecutive bases is a codon, we replace each by the codon provided in the table.
- Below are the top strands for the mRNA and the amino acid sequence:
+1: 5'-cgu aug cua aua cca ugu ucc gcg uau aac cca gcc gcc agu ucc gcu ggc ggc auu uua-3'
R M L I P C S A Y N P A A S S A G G I L
+2: 5'-c gua ugc uaa uac cau guu ccg cgu aua acc cag ccg cca guu ccg cug gcg gca uuu ua-3'
V C Stop Y H V P R I T Q P P V P L A A F
+3: 5'-cg uau gcu aau acc aug uuc cgc gua uaa ccc agc cgc cag uuc cgc ugg cgg cau uuu a-3'
Y A N T M F R V Stop P S R Q F R W R H F
Translating mRNA to amino acid sequences using -1, -2, and -3 reading frames uses a similar process to what was described above. The only difference is that since we are looking at the complementary mRNA strand (whose direction is would be 3' to 5'), we have to reverse the strand so that the direction is 5' to 3' and finding the complementary of the resulting strand. Then, the -1 reading frame is the same as +1, and -2 and -3 are read the same as +2 and +3 respectively.
- Below are the bottom strands for the mRNA and the amino acid sequence:
-1: 5'-uaa aau gcc gcc agc gga acu ggc ggc ugg guu aua cgc gga aca ugg uau uag cau acg-3'
Stop N A A S G T G G W V I R G T W Y Stop H T
-2: 5'-u aaa aug ccg cca gcg gaa cug gcg gcu ggg uua uac gcg gaa cau ggu auu agc aua cg-3'
K M P P A E L A A G L Y A E H G I S I
-3: 5'-ua aaa ugc cgc cag cgg aac ugg cgg cug ggu uau acg cgg aac aug gua uua gca uac g-3'
K C R Q R N W R L G Y T R N M V L A Y
- +1, -2, and -3 are open reading frames since they do not contain a "Stop" codon.
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