Experimental Work
Nirenberg and Leder could not decode the remaining codons in the same manner as Nirenberg did with Mattaei. Because the mRNA bases were taken up at random by the ribosome, it is hard to determine which specific codon correlates with the amino acid. For example, to pick out the correct codon among non repeating codons (UCU, CUU, UUC) is difficult because they couldn't determine the specific sequence. Instead, Leder and Nirenberg used very short artificial RNA sequences (three nucleotides) in the cell-free systems. These shorter length fragments were long enough to allow the ribosome to bind with the type of tRNA molecule that is complementary to the one codon and still be detectable. The key step of the experiment was that they labeled one type of amino acid at a time and then put the mixture through a Millipore filter. This special filter allowed unbound tRNAs to pass through but did not allow the ribosomes with the bound triplet to pass through. The sample was then tested for radioactivity. If there was radioactivity found in the sample that did not pass through the filter the corresponding Amino acid was added.
Read more about this topic: Nirenberg And Leder Experiment
Famous quotes related to experimental work:
“Experimental work provides the strongest evidence for scientific realism. This is not because we test hypotheses about entities. It is because entities that in principle cannot be ‘observed’ are manipulated to produce a new phenomena
[sic] and to investigate other aspects of nature.”
—Ian Hacking (b. 1936)