Hfr Mapping Problem
An Hfr E. coli contains the following genetic traits: kans, lac+ , his+ , trp+ , ampr . It is mated with a recipient E. coli that contains the opposite genetic traits for those traits listed abov: kanr. lac- , his- , trp- , amps . Assume all other catabolic and biosynthetic genes are present in both strains. Note that kanS means the absence of the kanamycin resistance gene in the Hfr strain, which will allow growth only of the recipient cells in the presence of kanamycin. This is necessary to select against the Hfr donor strain as you are monitoring which genes transferred to the recipient.
At periodic intervals, conjugation is disrupted and cells are plated onto several types of defined media. Nothing grows at the beginning of the experiment on media containing lactose, kanamycin, and ampicillin as this is the most selective medium, but all cells grow on complex media containing no ampicillin (the least selective medium). Mating is interrupted at the times listed below and the following are some of your observations of growth characteristics on a few of the selective media plates containing the indicated nutrients/antibiotics:
15 min.
Growth on defined media containing: kanamycin, glucose, histidine (does not contain tryptophan).
No growth on defined media containing: kanamycin, lactose (sole carbon source), tryptophan, histidine.
30 min.
Growth on defined media containing: kanamycin, lactose (sole carbon source), histidine (does not contain tryptophan).
No growth on defined media containing: kanamycin, glucose, tryptophan (does not contain histidine).
No growth on defined media containing: kanamycin, ampicillin, lactose (sole carbon source), histidine, tryptophan.
45 min.
Growth on defined media containing: kanamycin, lactose (sole carbon source) (does not contain histidine or tryptophan).
No growth on defined media containing: kanamycin, ampicillin, lactose (sole carbon source), histidine (does not contain tryptophan).
60 min.
Growth on defined media containing: kanamycin, lactose (sole carbon source) (does not contain histidine or tryptophan).
No growth on defined media containing : kanamycin, ampicillin, lactose (sole carbon source) (does not contain histidine or tryptophan).
Hfr Mapping Problem
An Hfr E. coli contains the following genetic traits: kans, lac+ , his+ , trp+ , ampr . It is mated with a recipient E. coli that contains the opposite genetic traits for those traits listed abov: kanr. lac- , his- , trp- , amps . Assume all other catabolic and biosynthetic genes are present in both strains. Note that kanS means the absence of the kanamycin resistance gene in the Hfr strain, which will allow growth only of the recipient cells in the presence of kanamycin. This is necessary to select against the Hfr donor strain as you are monitoring which genes transferred to the recipient.
At periodic intervals, conjugation is disrupted and cells are plated onto several types of defined media. Nothing grows at the beginning of the experiment on media containing lactose, kanamycin, and ampicillin as this is the most selective medium, but all cells grow on complex media containing no ampicillin (the least selective medium). Mating is interrupted at the times listed below and the following are some of your observations of growth characteristics on a few of the selective media plates containing the indicated nutrients/antibiotics:
15 min.
Growth on defined media containing: kanamycin, glucose, histidine (does not contain tryptophan).
No growth on defined media containing: kanamycin, lactose (sole carbon source), tryptophan, histidine.
30 min.
Growth on defined media containing: kanamycin, lactose (sole carbon source), histidine (does not contain tryptophan).
No growth on defined media containing: kanamycin, glucose, tryptophan (does not contain histidine).
No growth on defined media containing: kanamycin, ampicillin, lactose (sole carbon source), histidine, tryptophan.
45 min.
Growth on defined media containing: kanamycin, lactose (sole carbon source) (does not contain histidine or tryptophan).
No growth on defined media containing: kanamycin, ampicillin, lactose (sole carbon source), histidine (does not contain tryptophan).
60 min.
Growth on defined media containing: kanamycin, lactose (sole carbon source) (does not contain histidine or tryptophan).
No growth on defined media containing : kanamycin, ampicillin, lactose (sole carbon source) (does not contain histidine or tryptophan).
