The following shows the genotype of a partial diploid bacterial cell - where one
ID: 62485 • Letter: T
Question
The following shows the genotype of a partial diploid bacterial cell - where one chromosomal region containing the lac operon in E,coli is given, and the other fragment is from a plasmid carrying another lac operon from another source. The two are separated by a slash (/).
The possible answers indicate with a + or a - whether -galactosidase would be expected to be produced at induced levels under two circumstances: 1) first in the absence of lactose and 2) second in the presence of lactose. (Assume that glucose is not present in the medium.)
Genotype G: I- Oc Z+/ F I- O+ Z+
KEY:
I+ = wild-type repressor
I- = mutant repressor (unable to bind to the operator)
Is = mutant repressor (insensitive to lactose)
O+ = wild-type operator
Oc = constitutive operator (insensitive to repressor)
Explanation / Answer
The cell is I- at both the loci. I- is recessive and allows expression of the Z both in the presence and in the absence of lactose.
Oc is constitutional mutation which means that the gene is expressed irrespective of the repressor.
Therefore, the enzyme is produced under both the conditions.
1. +
2. +