A study was conducted in an attempt to determine which functional regions of a particular conjugative transfer gene (tra1) are involved in the transfer of plasmid R27 in Salmonella enterica. The R27 plasmid is of significant clinical interest because it is capable of encoding multiple-antibiotic resistance to typhoid fever. To identify functional regions responsible for conjugal transfer, an analysis was conducted by Lawley et al. (2002). J. Bacteriol. 184:2173-2180 was conducted in which particular regions of the tra1 gene were mutated and tested for their impact on conjugation. Shown here is a map of the regions tested and believed to be involved in conjugative transfer of the plasmid. Similar coloring indicates related function. Numbers correspond to each functional region subjected to mutation analysis.

Accompanying the map is a table showing the effects of these mutations on R27 conjugation.


Effects of Mutations in Functional Regions of Transfer Region 1 (tra1) on R27 Conjugation



Which regions appear to have a limited impact on conjugation?

Verified step by step guidance

1. Examine the table showing the effects of mutations in each functional region of the tra1 gene on the conjugative transfer frequency of the R27 plasmid. Note the relative conjugation frequency (%) for each region.
2. Identify regions where mutations result in a conjugation frequency close to 100%, indicating that these mutations do not significantly impair conjugation. According to the table, these are regions 1, 2, and 4.
3. Compare these regions to the map to understand their functional grouping and color coding, which may provide insight into their related functions and why mutations in these regions have limited impact.
4. Recognize that regions with conjugation frequencies near zero or very low values indicate critical roles in conjugation, so regions with high frequencies are less critical or have redundant functions.
5. Conclude that regions 1, 2, and 4 appear to have a limited impact on conjugation based on their mutation effects, as their relative conjugation frequencies remain at 100%.

Key Concepts

Conjugative Transfer and Plasmid Function

Conjugative transfer is a process where genetic material, typically plasmids, is transferred between bacteria through direct contact. Plasmids like R27 carry genes that can confer antibiotic resistance, making their transfer clinically significant. Understanding which gene regions affect this transfer helps identify targets to control the spread of resistance.

Functional Regions and Mutation Analysis

Genes can be divided into functional regions, each responsible for specific roles in a biological process. Mutation analysis involves altering these regions to observe changes in function, revealing which parts are essential. In this study, mutations in tra1 regions were tested to determine their impact on plasmid conjugation efficiency.

Interpreting Conjugation Frequency Data

Conjugation frequency measures how effectively a plasmid is transferred between bacteria. A relative frequency of 100% indicates normal transfer, while 0% means transfer is blocked. Regions with mutations showing near 100% frequency have limited impact on conjugation, whereas those with 0% are critical for transfer.