Question

Outline the steps involved in mapping a bacterial chromosome by conjugation

Answer 1

The bacterial chromosome is mapped through conjugation by creating an Hfr strain, mating it with an F- cell, disrupting the conjugation at timed intervals, culturing the recipient cells, and analyzing gene transfer to determine the location of genes on the bacterial chromosome.

Step-by-step explanation:

Mapping a bacterial chromosome through conjugation involves several steps, primarily utilizing the natural process by which bacteria exchange genetic material. In the context of an Escherichia coli (E. coli) experiment, these steps typically include the following:

1. An Hfr (High-frequency recombination) cell, which has an F plasmid integrated into its chromosome, forms a sex pilus with a recipient F- cell.
2. This establishes a conjugation tube, allowing for the unidirectional transfer of genetic material starting from the integration site of the F plasmid via a process called rolling circle replication.
3. Conjugation is typically interrupted at various time intervals, and recipient cells are cultured and analyzed for the presence of donor genetic material, providing data on which genes were transferred.
4. The order and timing of gene transfer provide information about the location of genes on the chromosome, enabling bacterial geneticists to map the bacterial chromosome by creating a genomic map based on transfer times measured in minutes.

These steps allowed for the mapping of genes before the widespread availability of bacterial genome sequencing and were instrumental in demonstrating the circular nature of the bacterial chromosome.