Final answer:
The question deals with mapping the E. coli chromosome using interrupted-conjugation experiments and Hfr strains, where the F plasmid is integrated into the bacterial chromosome, transferring genes in a linear fashion to an F- strain. A comprehensive map is created based on the order of gene transfer and the time it takes, which correlates with gene position and size.
Step-by-step explanation:
The question relates to the mapping of genes on the E. coli chromosome using Hfr strains. When an F plasmid integrates into the bacterial chromosome, Hfr cells can transfer parts of the E. coli DNA to an F- cell through a mating bridge. As the integrated F plasmid behaves like a large F plasmid, the genes closest to the integration site are transferred first during rolling circle replication, which allows for the mapping of the genetic material based on the time of conjugation.
Interrupted-conjugation experiments with different Hfr strains have shown that when an F plasmid is integrated into the bacterial chromosome, the genes are transferred linearly. The time it takes for a gene to be transferred reflects both its position on the chromosome and its length. With enough data from various Hfr strains, a comprehensive map of the E. coli chromosome can be created, showing the order of the genes and their relative distances.
In the hypothetical experiment for this question, the order of genes transferred would need to be determined by the specific entry times provided for each marker from strains A through E. Unfortunately, as the entry times and the number of markers are not provided in the question, a complete map cannot be constructed. However, the principle remains that the timing of conjugation can be used to map the E. coli genome in minutes, based on the time it takes for the entire genome to be transferred during conjugation.
Based on the information provided, we can map the F+ strain of E. coli by analyzing the order of gene transfer during conjugation experiments using different Hfr strains. The chart shows the entry times of the first five markers into an F- strain. From this data, we can determine the positions of all genes and their distances apart in minutes.
In the experiment with Hfr4, the order of gene transfer after longer times of conjugation was found to be: V-W-X-Y-Z-A-B. This provides a basis for constructing the map of the F+ strain.
Genes are arranged linearly on the bacterial DNA, with the time to transfer a complete gene reflecting its size (length). By analyzing the timing of conjugation, we can determine the gene locus and the size of genes.