After performing a Lys operon mRNA Northern blot and Western blot of the two oth

Question

After performing a Lys operon mRNA Northern blot and Western blot of the two other proteins expressed from the same mRNA, LysD and LysE, your results are as follows

You proceed to determine the sequence of the entire mRNA and its structure is as below

I = Lys repressor gene;

D, E, F = Lys operon structural genes;

P = Lys promoter;

O = Lys operator

Briefly explain how the mRNA sequence was determined

Explanation / Answer

In this a Lys Operon mRNA Northern blot and Western blot is performed for two other proteins that is expressed from same mRNA, LysD and LysE. The Northern and western blot helps in showing regulation of lysine biosynthetic genes. It is observed that the amino acid presence does not regulate the Lys Operon transcription. From the western blots of Lys A and Lys C it shows that Lys A and Lys C is regulated post-transcriptionally. It also reduces the protein expression in presence of amino acid and the expression of protein is high in absence of amino acids. By sequencing, we find that there is short ORF upstream of the three Lys biosynthetic genes. The size of the RNA might be change depending on presence of amino acids if the operon was regulated through transcriptional attenuation.

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