A mutant strain of E. coli is found that produces both beta-galactosidase and permease at high
levels whether lactose is present or not.
(a) What are two possible genotypes for this mutant?
Another mutant is isolated that produces no beta-galactosidase at any time but produces
permease if lactose is present in the medium. A merodiploid strain is formed from these two
mutants. in the absence of lactose, neither beta-galactosidase nor permease is made. When
lactose is added, the merodiploid strain makes both beta-galactosidase and permease.
(b) What is the genotype of the merodiploid strain?
Solution
A mutant of E. coli is found that produces both beta - galactosidase and permease at high levels
in the presence or absence of lactose
a) The two possible genotypes for this mutant is given as-:
F+ Z+ Y+
Now another mutant is isolated that produces no beta-galactosidase at any time but produces
permease if lactose is present in the medium.
The genotype for this mutant is given as-:
F- Z- Y-
Given a merodiploid strain is formed from these two mutants.
Merodiploid is partially diploid bacterium having its own chromosome and a fragment that is
introduced either by conjugation, transformation or transduction. It is given by-:
F+ Z+ Y+ x F- Z- Y-
=F\' Z+ - Y-
b) The genotype for the merodiploid strain is F\' Z+ - Y-
For Merodiploid strain in the absence of lactose, neither beta-galactosidase nor permease is
formed but in the presence of lactose both beta-galactosidase and permease is produce.
As mutant 1 have the ability to make beta-galactosidase in the absence or presence of lactose but
the mutant 2 is unable to make beta-galactosidase at any time so in the new mutant the gene for
beta galactosidase is expressed only in the presence of lactose.
Also the permease producing gene of 2 mutant is dominant that is the reason the merodiploid
strain produces permease in the presence of lactose but not in the absence of lactose..
A mutant strain of E. coli is found that produces both beta-galactos.pdf
1. A mutant strain of E. coli is found that produces both beta-galactosidase and permease at high
levels whether lactose is present or not.
(a) What are two possible genotypes for this mutant?
Another mutant is isolated that produces no beta-galactosidase at any time but produces
permease if lactose is present in the medium. A merodiploid strain is formed from these two
mutants. in the absence of lactose, neither beta-galactosidase nor permease is made. When
lactose is added, the merodiploid strain makes both beta-galactosidase and permease.
(b) What is the genotype of the merodiploid strain?
Solution
A mutant of E. coli is found that produces both beta - galactosidase and permease at high levels
in the presence or absence of lactose
a) The two possible genotypes for this mutant is given as-:
F+ Z+ Y+
Now another mutant is isolated that produces no beta-galactosidase at any time but produces
permease if lactose is present in the medium.
The genotype for this mutant is given as-:
F- Z- Y-
Given a merodiploid strain is formed from these two mutants.
Merodiploid is partially diploid bacterium having its own chromosome and a fragment that is
introduced either by conjugation, transformation or transduction. It is given by-:
F+ Z+ Y+ x F- Z- Y-
=F' Z+ - Y-
b) The genotype for the merodiploid strain is F' Z+ - Y-
For Merodiploid strain in the absence of lactose, neither beta-galactosidase nor permease is
formed but in the presence of lactose both beta-galactosidase and permease is produce.
As mutant 1 have the ability to make beta-galactosidase in the absence or presence of lactose but
the mutant 2 is unable to make beta-galactosidase at any time so in the new mutant the gene for
beta galactosidase is expressed only in the presence of lactose.
Also the permease producing gene of 2 mutant is dominant that is the reason the merodiploid
strain produces permease in the presence of lactose but not in the absence of lactose.
