(9 Pts) In E. coli, three closely linked loci have been identified. The loci are
ID: 220265 • Letter: #
Question
(9 Pts) In E. coli, three closely linked loci have been identified. The loci are symbolized by p, d and q. Wild type alleles are superscripted with a plus, while mutant alleles are superscripted with a minus. When an inducer is present or absent, the level of Enzyme X is measured and the results for several different strains are given below From the information given, determine which of the genes is the regulator gene, which is the operator and which is the structural gene for Enzyme X. Note: There are no super-repressor mutants and assume all promoters are wild type! Phenotype (level of Enzyme X) Absence of Inducer Presence of Inducer Genotype p+d-q+ p- d+qt p+ d+q- p+ d+ q+/p- d-q- p+d-9+/p-d+q none none high high none high high high none high none high lg ig high high high lg p-d+q+/p+ d-q-Explanation / Answer
When d is absent, no enzyme is made. So, d can not be the regulator gene (repressor). It can be the structural gene.
When p is absent, the enzyme is synthesized irrespective of the presence or absence of inducer. So, p must be the regulator gene that can sense and respond to the inducer. Since p is a trans-acting factor, it can be complemented.
When q is absent, the enzyme is synthesized irrespective of the presence or absence of inducer. So, q must be the operator sequence that can be bound by the repressor. Since d is a cis-acting factor, it can not be complemented.
d = Structural gene
p = Regulatory gene
q = Operator sequence
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.