Question

Sam is working in a genetics lab this summer in order to gain more hands-on experience before he applies to graduate school. The professor with whom he is working is particularly interested in studying a new strain of E.coli and assigns Sam an interrupted mating experiment to perform. Sam is attempting to determine the order of 7 different genes on the bacterial chromosome: Ger, Fra, Lod, Moc, Bla, Jat, and Arp. Sam used four different Hfr strains (Hfr 1, Hfr2, Hfr3, Hfr4) in order to help him determine the gene order. He observed that the Hfr strains transferred genes at the times shown below. However, Sam is a little forgetful and neglected to record the times at which several of the genes were transferred. Afraid that the professor will become angry with him, Sam comes to you for assistance. 1 6 Jat 17 Bla A. (0.5 pt. each; 2 pts. total) Based upon what you know about bacterial genomes and interrupted mating experiments, fill in the missing four pieces of missing data in the table below. Strain 1 (Hfr1) Strain 2 (Htr2) Strain 3 (Hfr3) Strain 4 (Hfr4) Gene Time Gene Time Gene Time Gene Time (minutes minutes) minutes) minutes) Moc 6 Bla Ger 3 Ger 18 Lod 7 Moc 18 Moc Lod 28 Ger Jat Ger 35 Bla Moc 29 Arp 46 Lod 45 Fra 38 Jat Fra 60 51 B. (6.5 pts, total) Us the data from the experiments above; draw a single circular map of the seven genes as they would appear on the E. coli chromosome. Be sure to include all of the following, using a format similar to that presented in class: Genes appear in the correct order (0.25 pt./gene position=1.75 pts. total) Distances between adjacent genes (in minutes) (Correct distances between genes = 0.25 pt. ea; 1.75 pts. total) Distance between genes and origin of transfer for each Hfr (in minutes) (Correct distance between integrated Hfr and first gene for each Hfr = 0.25 pt. each, 1 pt. total) Location of each of the 4 integrated F factors (origin and direction of transfer for each Hfr) (Correct position and orientation Hfr 0.5 pt. ea.; 2 pts, total) Please draw your diagram below. .

Answer 1

Strain 1 (Hfr 1)	Strain 2 (Hfr 2)	Strain 3 (Hfr 3)	Strain 4 (Hfr 4)
Gene	Time (in minutes)	Gene	Time (in minutes)	Gene	Time (in minutes)	Gene	Time (in minutes)
Moc	6	Bla	1	Ger	6	Jat	3
Ger	18	Lod	7	Moc	18	Moc	23
Lod	28	Ger	17	Jat	38	Ger	35
Bla	34	Moc	29	Arp	46	Lod	45
Fra	38	Jat	49	Fra	60	Bla	51

From Strain 2 , we can infer that the distance between Bla and Lod genes is 6 minutes. Thus we use this information to get the distance of Bla gene from Origin of transfer in Strain 1. In Strain 1, the distance of Lod gene from origin of transfer is 28 mins. Thus distance of Bla gene will be = 28 + 6 = 34 minutes.

From Strain 1 , we can infer that the distance between Ger and Moc genes is 12 minutes. Thus we use this information to calculate the distance of Moc gene from the origin of transfer for Hfr 4. The distance of Ger gene from the origin of transfer is 35 mins. Thus the distance of Moc gene from origin of transfer can either be 35 + 12 = 47 or 35 - 12 = 23, since Moc gene can be on the either of side of Ger gene owing to the circular nature of the E.coli chromosome. However we observe that the distance is increasing from top to above i.e. from Jat to Bla and Moc gene comes above Ger gene. So distance of Moc gene from origin off transfer must be lower than Ger gene . So distance of Moc gene will be equal to 23 mins.

From Strain 4, we can infer that the distance between Jat and Moc gene is = 23 - 3 = 20 minutes. So distance of Jat gene from origin of transfer in Strain 3 will be = 18 mins + 20 mins = 38 mins.

Similarly the distance of Jat gene from origin of transfer in case of Strain 2 will be = 29 + 20 = 49 mins.

Following the above 4 tables for 4 different strains ,we calculated the distance between other 7 genes :

From Strain A, we can obtain the following:

The distance between Moc - Ger is 18 - 6 = 12 minutes.

The distance between Ger and Lod gene is 28 - 18 = 10 minutes

The distance between Lod and Bla gene is 34 - 28 = 6 minutes.

The distance between Bla and Fra gene is 38 - 34 = 4 minutes.

For Strain 2, the direction of origin of transfer is clockwise. In this fashion, we can see that the new Jat gene is the last to come after 49 minutes and is after Moc gene. Thus we incorporate it next to Moc gene at a distance of 20 minutes in a anti-clockwise fashion.

For strain 3, the direction of origin of transfer is clockwise. In this fashion, we can see that the new Arp gene comes after the Jat gene at 46 minutes. Thus we place the Arp gene at a distance of 8 minutes (46 minutes - 38 minutes) from Jat gene by moving anticlockwise from Jat gene.

Next we observe in the same strain 3, that Fra gene is the last to come and is after Arp gene at a distance of (60 - 46 ) = 14 mins. Thus we place the Fra gene in an anticlockwise direction from Arp gene at a distance of 14 minutes.

In the below image, the origin of transfer and direction of transfer is shown by an arrow. The direction of arrow signifies the direction of transfer and its position signifies the origin of each F factor. The distance between the genes are mentioned in minutes.

Horel بیا ایر S 2o mins. Ger for 3 Jat Tuice it for 4 8 Lod. sulle chur 6 #fore 2 Suicy Bla fra 4 mins. و إيا 5