Yon are working with a bacterium called Streptomyces coelicolor. Two genes, s co
ID: 217265 • Letter: Y
Question
Yon are working with a bacterium called Streptomyces coelicolor. Two genes, s contained within a single operon. skyl and sky2 encode two enzymes that are both required to produce blue color. Expression of skyl and sky2 is dependent on the presence of a compound in growth medium A: on growth medium A, the colonies are blue; on growth medium B, the colonies ky! and sky 2, are are white. You discover two mutants (regI' and reg2) that cause constitutive expression of the sky operon resulting in blue colonies on growth medium B. One of the reg mutants contains a defect in a DNA- binding site in the sky operon, and the other contains a loss-of-function mutation in the gene encoding a DNA-binding protein that binds to the DNA-binding site and regulates shy operon expression. a. 1s the DNA-binding protein a positive or negative regulator of the sky operon? (0.4 pts) To determine which mutant has a defect in the DNA-binding site and which has a defect in the binding protein, you decide to do partial diploid analysis. The phenotype that you analyze is the b. production of blue color on growth medium B. i. If reg2 encodes the regulatory protein and regl is the DNA-binding site, what results (blue or white colonies) would you predict for the following strains? (0.-4 pts each, 0.8 pts total) regl reg2 shyl" shy2 IF' reg!' reg2" skyl' sky2 regl' reg? skyl sky2 /F reg! reg2 skyl sky2 ii. Ifregl encodes the regulatory protein and reg2 is the DNA-binding site, what results (blue or white colonies) would you predict for the following strains on growth medium B? (0.4 pts each, 1.6 pts total) regl reg?' skyl sky2 IF regl reg2 skyl' sky2 regl reg2' skyl' sky2 iF reg!" reg?' shyl' sky2 regl' reg2 skyl shyiF'regl reg2 skyl sky2 regl reg? skyl" sky2"/F' regl reg2" skyl sky2Explanation / Answer
a. DNA binding protein binds to the DNA and inhibit the expression of Operon. This idea is derived from the line in which it is given that the mutation in this protein leads to constitutive expression means we can see generally this protein is involved in the negative regulation of operon.
Generally this protein is involved in the inhibition of Operon. And mutation in this protein leads to constitutive expression of genes or Operon.
b.
1. First: it becomes normal and the colonies are white in normal condition.
Providing genes of regulatory protein, regulatory proteins are synthesized and then take part in normal processing of Operon.
Second: when we give DNA binding domain coding region by other, than it is not able to produce normal genotype and phenotype.
So the colonies are blue and not normal genotype phenotype.
2.
First: image is not clear positive and negative symbols are not visible clearly.
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