2. Select the vector. A. PCR wild-type repressor t repressor (unable to bind to
ID: 174620 • Letter: 2
Question
2. Select the vector.
A. PCR wild-type repressor t repressor (unable to bind to the operator) ls nt repressor (insensitive to lactose) o+ wild-type operator OC constitutive operator (insensitive to repressor) Will a bacterial cell with the following partial hybrid DNA constitution produce any Beta-galactosidase, first in the presence of lactose sugar, and then in the absence of lactose sugar? (he first part below before the slash is the chromosome and the second part after the slash is the plasmid; F' plasmid DNA. O No, yes O Yes, no O Yes, yes o Not possible to determine O No, noExplanation / Answer
The answer for first portion is Yes, Yes.
The repressor protein binds to operator sequence of lac operon and inhibits the expression of belta-galactosidase. This happens in presence of glucose and absence of lactose is present in the medium. In presence of lactose and absence of glucose, lactose binds to repression protein and dislodges it from operator and RNA polymerase performs the transcription of lac operon.
Now in the current situation, where the genotype is
Is(Insensitive to lactose)
Oc(Constitutive operator, insensitive to operator)
Z+(wild betaglactosidase)
With F’ I+ O+ Z+
The mutation Oc would lead to constitutive expression of betaglactosidase both in the presence and absence of lactose. The F’ segment would be totally non-functional as Is(Insensitive to lactose) would remain bound to O+ both in presence or absence of lactose.
Finally, in any of the situation the betaglactosidase will be expressed from the genomic DNA.
Answer 2 Plasmid are referred as vector and carry genetic information apart from chromosomal DNA. They serve as vehicle to carry foreign gene and used for artificially manipulating the wild genotypes of bacteria, plants, or animals.
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