Utilization of galactose, in bacteria requires activation of the gal operon (gal
ID: 89969 • Letter: U
Question
Utilization of galactose, in bacteria requires activation of the gal operon (galETK).The protein GalR binds to a sequence near the promoter of the gal operon, inhibiting binding of Polymerase when galactose absent. a. What is the function of GalR? b What kind of sequence will GalR bind? c. Is the regulation described in (b) positive or negative? d. If transposon, a mobile genetic element inserts itself in the middle of the galR gene, how would this affect the expression of the gal operon? e. When galactose is present, it binds to GalR and inactivates it. What type of regulatory molecule is galactose? f. The gal operon is not activated unless the cells are starved for glucose. By analogy to our previous discussions of carbohydrate operons, which other regulatory molecules would be required for the expression of the gal operon? g. Is the regulation described in positive or negative? You have two samples of DNA. Sample 1 is exposed to high temperature (about 95 degree C). Sample 2 is treated with an exonuclease. Based on what you know about the structure of DNA, what would you have left in each sample after the treatment described above? In sickle cell anemia you have a base change that creates a D7V mutation. After you PCR up the individual's genome, you create a genetic map (shown below). Name and describe a molecular genetic technique, in which you could determine if the mom has the recessive (both genes knocked out sickle trait or not. Be sure to state your positive control.Explanation / Answer
37) Gal operon encodes enzymes necessary for galactose metabolism. It contains two operators: external and internal.
a) GalR functions as a repressor in the Gal operon.
b) GalR acts by binding to the operator site.
c) The regulation described above in Gal operon by GalR is negative
d) If a transposon is introduced in the middle of GalR gene, it can cause mutation of GalR gene. It no longer binds to the operator region and acts as a repressor. Gal operon will start producing enzymes for galactose metabolism even in the absence of galactose.
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