Hello I\'m having understand the concept of this problem. Like first of all what

Question

Hello I'm having understand the concept of this problem. Like first of all what is the difference between a- & a+ and for b and c. Does it when it's a "+" that it's present? and when it's "-" that it's absent? Also on the right side what does it when it says inducer is absent or present? I know when the inducer is present the repressor can't bind to the operator so Z gene is made hence why it's "+" for line 1(a-b+c+). When the inducer is absent for that same line 1 how is it that Z gene is made when the repressor can bind to the operator? It's probably just me and just over thinking this question but can someone please break down for me how to understand this question and how to solve it!

4. The genes shown in the following table are from the lac operon system of E. coli. The e o gene (Z) for B-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 Z gene Inducer absent Inducer present Genotype a-b+c+ a +b+c- a +b-c- a+b +c+/a-b-c- a+b+c-Va-b-c+ a-b+c+/at-b-c- State which symbol (a, b, or c) represents each of the lac I, operator region and gene Z. SHOW YOUR WORK. lacz (from line 1, 2 and 30 c lacI (from line 60 operator

Explanation / Answer

Since mutation in a and c give constitutive mutants while mutation in b causes no production of enzyme at all. This means that "b" refers to lac z gene and "a" and "c" are either repressor or operator regions. Since mutation in operator regions are cis dominant and gives constitutive mutants only when present on same chromosome. Line 6 has mutant c and wild type b on the same chromosome while the phenotype is inducible wild type c is present in trans position. Line 7 exhibits mutant a and wild type b on the same chromosome and give constitutive phenotype. This indicates that "a" is operator region and c is repressor while b is lac Z.

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