Does Colony color yields direct information about the state of the lacZ gene
Added by Austin V.
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The lacZ gene encodes the enzyme β-galactosidase, which is responsible for breaking down lactose into glucose and galactose. It is often used as a reporter gene in molecular biology. Show more…
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X-gal is a colorless, lactose-like molecule that can be split into two fragments by $\beta$ -galactosidase. One of these product molecules is blue. The following photograph shows $E$. coll colonies growing in a medium that contains X-gal. Find three colonies whose cells have functioning copies of \beta-galactosidase. Find three colonies whose cells might have mutations in the $\operatorname{lac} Z$ or in the lacY genes. Suppose you analyze the protein-coding sequence of the $\operatorname{lac} Z$ and $\operatorname{lac} Y$ genes of cells from the three mutant colonies and find that these sequences are wild type (normal). What other region of the lac operon might be altered to account for the mutant phenotype of these colonies?
Carefully consider the result shown in Figure $Q5-13$ Each of the two colonies shown on the left is a clump of approximately 100,000 yeast cells that has grown up from a single cell, which is now somewhere in the middle of the colony. The two yeast colonies are genetically different, as shown by the chromosomal maps on the right. The yeast Ade2 gene encodes one of the enzymes required for adenine biosynthesis, and the absence of the Ade2 gene product leads to the accumulation of a red pigment. At its normal chromosome location, Ade 2 is expressed in all cells. When it is positioned near the telomere, which is highly condensed, Ade 2 is no longer expressed. How do you think the white sectors arise? What can you conclude about the propagation of the transcriptional state of the Ade2 gene from mother to daughter cells?
Adi S.
X-gal is a colorless, lactose-like molecule that can be split into two fragments by $\beta$ -galactosidase. One of these product molecules is blue. The following photograph shows $E$, coli colonies growing in a medium that contains X-gal. Find three colonies whose cells have functioning copies of \beta-galactosidase. Find three colonies whose cells might have mutations in the $\operatorname{lacZ}$ or in the lacY genes. Suppose you analyze the protein-coding sequence of the lacZ and lacY genes of cells from the three mutant colonies and find that these sequences are wild type (normal). What other region of the lac operon might be altered to account for the mutant phenotype of these colonies?
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