● The Genetic Code
○ Proteins are made from 20 Nucleotides
● Defining a Codon
○ Glasow stated that the Nucleotides must be in 3 base codes
■ Multiple unique triplets would code for the same Amino Acid
● Deciphering the Code
○ Researchers took simple mRNA proteins and saw what they coded for
○ Marshall Nerenberg and Johann Mattaei
■ All the components they believed were necessary for Protein synthesis
into tubes
● RNA Template, nucleotides, Ribosomes, Amino acids, and an
energy source
■ Started by making a simple Nucleic acid made of Uracils
● Produced a repeating simple polypeptide sequence - identical
amino acids
○ Created Phenylalanine
■ Follow up research used alternating Uracil and Cytosines
●
● Always resulted in a string of Leucine and Serine
● Confirmed 3 nucleotides result in a Codon
● The standard code
○ Codons are written 5’ to 3’ position
, ■ Codons on the coding strand = non-template strand
■ Non template strand has the same Nucleotides as the mRNA
○ Only AUG (Methionine) starts
○ UAA, UAG, and UGA = Stop
■ Translation stop Codons
○ Complementary = Antiparallel RNA
○ RNA Polymerase copies DNA template strand
■ Template Strand = Non-coding
■ Non template Strand = Coding strand
■ Open Reading frame = From AUG to one of the end Codons
○ Crick and shit
■ Proved that a sequence was written with 3 nucleotides
■ A single addition of a nucleotide = the code was misread
● Frameshift Mutations
■ 3 nucleotides removed or added = no Frameshift
● Most of the polypeptide conserved
● RNA
○ tRNA act as the intermediary between the mRNA and the polypeptide
■ Translators between the two codes
■ rRNA - machinery that facilitates this process
○ RNA molecules can serve as catalytic molecules
■ Some type of ancestral RNA was the precursor to current life
■ Needs further evidence
T2M3
, ●
○ tRNA
■ tRNA transfers cytoplasmically situated amino acids to a growing
polypeptide strand in a Ribosome
■ Each tRNA contains
● Single RNA strand
● 70-90 nucleotide length
● A lot of complementarity along the tRNA
○ Many structures have hydrogen bonds
○ Makes the helical segments and 3 loops
○
○ Anticodon region:
■ Nucleotide triplet that forms complementary
base pairs with a mRNA codon