Mapping bacterial genomes In classical genetics, what key information is generated by interrupted mating (Hfr × F−) experiments that stop conjugation at timed intervals?

Introduction / Context:Before whole-genome sequencing, geneticists used conjugation-based methods to infer gene order and relative distances on bacterial chromosomes. Interrupted mating of Hfr donors with F− recipients was a pivotal approach to build chromosome maps in organisms like Escherichia coli.

Given Data / Assumptions:

• Hfr strains transfer chromosomal genes to F− cells starting near the integrated F factor.
• Blender or mechanical shear is used to stop mating at precise times.
• Selectable markers allow scoring of which donor genes have entered the recipient at each time point.

Concept / Approach:

Because transfer proceeds linearly with time from the origin of transfer, earlier-entering genes are closer to the origin and later-entering genes are farther. By plotting gene entry times, researchers deduce gene order and construct time-of-entry maps, which convert to map units (minutes) on the circular chromosome.

Step-by-Step Solution:

Verification / Alternative check:

Independent mapping with phage transduction (co-transduction frequencies) and transformation can confirm local gene order, cross-validating interrupted mating maps. Agreement among methods supports the resulting chromosome map.

Why Other Options Are Wrong:

• DNA homology levels: Measured by hybridization or sequence alignment, not by interrupted mating.
• DNA sequences: Require sequencing technologies, not conjugation timing.
• Proteomics and metabolite flux: Determined by mass spectrometry or metabolic assays, not mating experiments.

Common Pitfalls:

• Assuming transfer speed equals physical distance directly; maps are relative “minutes,” not base pairs.
• Ignoring that origin and orientation depend on the integration site of the F factor in each Hfr strain.

Final Answer:

Bacterial genome maps