Partial genetic maps of the chromosomes in an Hfr strain and F- strain are shown below:
pro- lac- ade+ pro+ lac- ade-
A series of conjugational crosses between these strains is done in order to map four different lac- alleles (#1-4). In each cross, the parents carry a different combination of lac alleles, but in every case pro+ lac+ ade+ recombinants are selected. (Student note: I'm not sure if there's a typo here or above, since there doesn't appear to be a lac+ allele in the above chromosomes. (But my confusion about this problem goes far beyond a possible typo.)) The Table below shows a number of such recombinants obtained in crosses involving each combination of parental lac alleles.
Recipient lac allele
Donor lac allele Lac-1 Lac-2 Lac-3 Lac-4
Lac-1 0 24 18 236
Lac-2 206 0 21 190
Lac-3 192 179 0 214
Lac-4 37 26 23 0
Analyze the data in the Table and determine the relative order of the four lac alleles with respect to the flanking pro and ade loci.
The answer is pro-3-2-1-4-ade, but I have no idea how it was obtained. I don't even know where to get started on a problem like this. I know what Hfr and F- cells are, but that's about the extent of my knowledge regarding this problem.
Thank you!© BrainMass Inc. brainmass.com October 9, 2019, 3:42 pm ad1c9bdddf
The expert examines conjugational cross and gene order. The relative order of the four lac alleles with respect to the flanking pro and ade loci is determined.