A conjugation experiment is performed to map the location of three genes involved in the ability to synthesize three amino acids, histidine (His), tryptophan (Trp), and leucine (Leu). An Hfr strain with genotype met-his+leu+trp+ is mated with a met+his-leu-trp- recipient. The met marker, which (confers the ability to synthesize the amino acid methionine) is known to be transferred very late. After a short mating the cells are broken apart and plated on four different growth media. The amino acids present in the growth medium and the number of colonies observed on each are the following:
His, Trp: 250
His, Leu: 50
Leu, Trp: 500
His only: 10
A) What is the order of injection of the genes?
Please provide explanation.
A conjugation experiment is performed to map the location of three genes involved in the ability to synthesize three amino acids, histidine (His), tryptophan (Trp), and leucine (Leu). An Hfr strain with genotype met-his+leu+trp+ is mated with a met+his-leu-trp- recipient. The met marker, which (confers the ability to synthesize the amino acid methionine) is known to be transferred very late. After a short mating the cells are broken apart and plated on four different growth media. The amino acids present in the growth medium and the number of colonies observed on each are the following:
His, Trp: 250
His, Leu: 50
Leu, Trp: 500
His only: 10
A) What is the order of injection of the genes?
Please provide explanation.
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An Hfr strain of genotype j+ k+ l+ m- strs is mated with an F- strain that is j- k- l- m+ strr. At a number of times after they are mixed, the culture is agitated to separate mating cells, which are then plated out on agar media of three types, where nutrient J allows the growth of j-cells, nutrient K of k-cells, nutrient L of l- cells, and nutrient M of m-cells. In the table below, â+â indicates the presence of streptomycin or the indicated nutrient, and â-â indicates its absence.
| Medium | Str | J | K | L | M |
| 1 | + | + | + | - | + |
| 2 | + | - | + | + | + |
| 3 | + | + | - | + | + |
a. What donor genes are being selected on each type of agar?
b. The following table shows the number of colonies on each type of agar for samples taken at the indicated times after the initiation of mating. Use this information to determine the order of genes j, k, and l.
| Sampling Time (min) | NUMBER OF COLONIES | ||
| Medium 1 | Medium 2 | Medium 3 | |
| 0 | 0 | 0 | 0 |
| 5 | 0 | 0 | 0 |
| 7.5 | 100 | 0 | 0 |
| 10 | 200 | 0 | 0 |
| 12.5 | 300 | 0 | 75 |
| 15 | 400 | 0 | 150 |
| 17.5 | 400 | 50 | 225 |
| 20 | 400 | 100 | 250 |
| 25 | 400 | 100 | 250 |
c. From each of the 25 minute plates, 100 colonies are picked and transferred to a dish containing agar with all the nutrients except M. The number of colonies that grew on these plates is 89 of the 100 colonies from Medium 1, 51 of the 100 colonies from medium 2, and 8 of the 100 colonies from the Medium 3 plate. Using this data, fit gene m into the sequence of j, k, and l. Briefly explain your reasoning.
