I need help with this problem

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Riyoku
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I need help with this problem

Post by Riyoku » Sun Apr 02, 2006 8:14 pm

The genes shown in the table below are from the lac operon system of E. coli. The symbols a, b, and c represent the prepressor (I) gene, the operator (O) region and structural gene (Z) for beta-galactosidase, although not necessarily in that order. Furthermore, the order in which the symbols are written in the genotypes is not necessarily the actual sequence in the lac operon.

Activity (+) or inactivity (-) of beta-galactosidase gene

Genotype........................Inducer absent........................Incuder present
a- b+ c+...................................+.............................................+
a+ b+ c-...................................+.............................................+
a+ b- c-.....................................-..............................................-
a+ b- c+/a- b+ c- .....................+.............................................+
a+ b+ c+/a- b- c-......................-..............................................+
a+ b+ c-/a- b- c+.......................-.............................................+
a- b+ c+/a+ b- c- .....................+.............................................+


State which symbol (a,b, or c_ represents each of the lac genes I, O and Z.

(Hint: a (+) symbol represent a functional gene and a (-) symbol represents a mutated, non-functional gene.)


~=== We tried to figure it out.... still haven't gotten there yet T_T ===~

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GreenDog
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Post by GreenDog » Mon Apr 03, 2006 11:10 am

b-Beta-Gal
c-Repressor
a-Operator
Look at the first two lines if a or c are gone the regulation doesn't work, it means that they are the regulatory factors.
Line 3 shows that when b is gone no B-gal is produced. It means that b is B-gal.
To establish which one is the repressor look at line 7 you can see that c is a trans acting factor.
It means that is the repressor.
a is then the Operator.
"When In Danger Or In Doubt Run In Circles Scream And Shout"
Lawrence J. Peter

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