1. In two closely related bacterial species, an operon with five structural genes is found on the chromosome, with the genes arranged in the same order. However, in species B, gene X, which is NOT present in species A, is found between genes 2 and 3 of the five gene sequence.
a. Draw a schematic representation of the two operons.
b. If gene X has no sequence homology to any other gene in species B, how might it have arisen?
c. If the nucleotide sequence of gene X is 72% identical t gene 2 in species B, how might it have arisen?
2. The -10 and -35 sequences in bacterial promoters are separated by about two turns of the DNA double helix (remember genetics?). How do you think transcription would be affected if a deletion were introduced such that the -35 sequence was moved to the -29 position?
3. In bacteria, genes within an operon are transcribed under the control of a single promoter and the primary mRNA transcript contains sequences that can be translated into each of the independent proteins. In some cases the first gene in the linear sequence appears to be transcribed at a much higher rate than the second and subsequent genes (i.e. many but not all mRNAs contain the sequences encoded by gene 2 and beyond).