Nostoc, a genus of cyanobacteria, uses the enzyme nitrogenase to fix nitrogen. N

Question

Nostoc, a genus of cyanobacteria, uses the enzyme nitrogenase to fix nitrogen. Nitrogenase and nitrogenase reductase are encoded by the genes nifH, nifD and nifK, which are in an operon. Expression of this operon is negatively regulated by the NifA protein; if ammonia is present, transcription of the nifHDK operon is repressed.

Fill in the blanks with the letter codes that represent the following sequence elements.

A. Promoter
B. NifA binding site
C. Shine-Dalgarno site
D. Start codon
E. Stop codon
F. Transcription terminator

Note that the order of the elements is important and the same element can be placed at multiple locations. 2 points for each blank.


5’________nifH_________ nifD__________ nifK_________3’

Letters can be used more than once as well
Thanks in advance guys

Explanation / Answer

Well For an operon, by definition, it has only 1 set of regulators for all the genes in that operon (meaning that regulator whether repressor or enhancer will regulate all the genes in that operon). Let 1 = first blank. 2 = second blank. 3 = 3rd blank, and 4 = 4th blank 1 = A, B, C, D (technically, regulators can be downstream as well, but it requires being much further downstream and tend to occur mostly in eukaryotes (not prokaryotes) 2 = E,D (every gene will ahve its own start and stop codons) 3 = E,D 4 = E, F

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