The lux operon of the bacteria species Vibrio fisheri contains genes required fo
ID: 265556 • Letter: T
Question
The lux operon of the bacteria species Vibrio fisheri contains genes required for production of light (bioluminescence). Transcription of the lux operon genes luxA and luxB is regulated by a chemical "Al." luxA and luxB encode the light-producing Luciferase enzyme, and strains with either a luxA- or luxB- mutation fail to produce light A. Consider the genotypes listed in the table below. m* is a new lux mutation that always produces light. Is the m* mutation dominant or recessive? (Circle one.) (2 points) B. From the information below, is the lux operon inducible or repressible? (Circle one.) (2 points) C. You hypothesize that m* affects a regulator of lux operon transcription and decide to use genetic analysis to determine whether it affects a protein or a DNA element. In spaces 1 and 2 of the table below, write two genotypes that will allow you to distinguish between these possibilities. (4 points) D. Imagine you discover that the m* mutation affects a DNA element. In spaces 3-6 of the table below, write the predicted bioluminescence activity for your genotypes. (- is inactive, t is active.) (2 points) E. Genetic analyses of the V fisheri lux operon were actually performed in E. coli. Although E coli do not normally produce light, they are capable of it when provided a plasmid containing V fisheri lux operon DNA. How could you introduce a plasmid into E. coli cells? (2 points) (Write one method.) Table Bioluminescence Genotypes Al level low Al level high m* luxA+ luxB+ 3 4 2 6Explanation / Answer
a) m* is a dominant mutation as the bioluminance can be observed at low AI concentration in m*luxA+ luxB+ genotype. This bioluminance is sustained when the strain is complemented merodiploid (m* luxA+ luxB+ / m+ luxA+ luxB+)
b) The lux operon is an inducible type as it needs high amounts of AI for bioluminance.
c) Two genotypes will be used:
i) m*luxA-luxB-
ii) m*luxA- luxB-/ m+ luxA+ luxB+
d)
i) m*luxA-luxB-
-
-
no bioluminance even in the presence of high levels of AI
ii) m*luxA- luxB- / m+ luxA+ luxB+=
-
+
bioluminance is observed only when high levels of AI are present. The strain shows complementation. It confirms m* is a mutation in regulatory DNA element of the operon
e) Transduction can be used for transformation of E.coli.
i) m*luxA-luxB-
-
-
no bioluminance even in the presence of high levels of AI
ii) m*luxA- luxB- / m+ luxA+ luxB+=
-
+
bioluminance is observed only when high levels of AI are present. The strain shows complementation. It confirms m* is a mutation in regulatory DNA element of the operon
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