Hfr strains that differ in integrated F factor orientation and site of integration are used to construct consolidated bacterial chromosome maps. The data below show the order of gene transfer for five strains.
Hfr Strain   Order of Gene Transfer (First → Last)
Hfr A        oriT–thr–leu–azi–ton–pro–lac–ade
Hfr B        oriT–mtl–xyl–mal–str–his
Hfr C        oriT–ile–met–thi–thr–leu–azi–ton
Hfr D        oriT–his–trp–gal–ade–lac–pro–ton
Hfr E        oriT–thi–met–ile–mtl–xyl–mal–str
Draw a consolidated map of the bacterial chromosome. (Hint: Begin by placing the insertion site for Hfr A at the 2 o'clock position and arranging the genes thr–leu–azi- . . . in clockwise order.)

Verified step by step guidance

1. Start by understanding the problem: The goal is to construct a consolidated bacterial chromosome map using the gene transfer orders provided by the five Hfr strains. Each strain transfers genes in a specific order starting from its oriT (origin of transfer). The orientation and site of integration of the F factor determine the order of gene transfer.
2. Place the insertion site for Hfr A at the 2 o'clock position on a circular map, as suggested in the problem. Arrange the genes transferred by Hfr A (thr–leu–azi–ton–pro–lac–ade) in a clockwise direction starting from oriT.
3. Analyze the gene transfer order for Hfr B (oriT–mtl–xyl–mal–str–his). Identify overlapping genes between Hfr A and Hfr B to determine their relative positions. Place the genes from Hfr B on the map, ensuring continuity with the genes already placed from Hfr A.
4. Repeat the process for Hfr C (oriT–ile–met–thi–thr–leu–azi–ton), Hfr D (oriT–his–trp–gal–ade–lac–pro–ton), and Hfr E (oriT–thi–met–ile–mtl–xyl–mal–str). For each strain, identify overlapping genes with previously mapped genes to determine their relative positions and orientations. Add these genes to the map while maintaining the circular structure.
5. Once all genes from the five Hfr strains are placed on the map, verify the continuity and consistency of the gene order. Ensure that the oriT sites and gene orientations align correctly for each strain. The final consolidated map should represent the complete bacterial chromosome with all genes in their correct positions and orientations.

Key Concepts

Hfr Strains

Hfr (high frequency of recombination) strains are bacterial strains that have the F factor integrated into their chromosome. This integration allows them to transfer chromosomal genes to a recipient bacterium during conjugation. The orientation and site of integration of the F factor can vary among different Hfr strains, affecting the order in which genes are transferred.

Gene Transfer Order

The gene transfer order refers to the sequence in which genes are transferred from the Hfr strain to a recipient bacterium during conjugation. This order is determined by the position of the F factor integration and the direction of replication. By analyzing the transfer order from multiple Hfr strains, researchers can deduce the relative positions of genes on the bacterial chromosome.

Consolidated Chromosome Map

A consolidated chromosome map is a visual representation of the relative positions of genes on a bacterial chromosome, constructed using data from various Hfr strains. By plotting the gene transfer orders from different strains, researchers can create a comprehensive map that illustrates the arrangement of genes, helping to understand genetic linkage and the organization of the bacterial genome.