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Hfr, F+, F', F-

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The following table contains statements pertaining to Hfr, F+, F', and/or F- strains of bacteria. Indicate in respective boxes if the statements apply to each category by putting Hfr, F+, F', F- beside the statement.

a) Contains genes that regulate conjugation and the transfer of DNA from one cell to another
b) Always acts as the recipient in conjugation
c) F factor is integrated into the host chromosome
d) Cannot form a pilus
e) F factor is in the plasmid form carrying a segment of chromosomal DNA

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The categorization of the F+ / F- and Hfr bacteria follows some pretty basic rules. Bacteria exchange some of their genetic material "horizontally" - they can pass genetic material from one bacterium to another via a process called conjugation. Only some bacteria can actually initiate this transfer however, and others tend to receive. The F-factor, or fertility factor, is a segment of genes which cumulatively give the bacterium the ability to initiate conjugation. This ...

Solution Summary

The expert examines the contained genes of regulated conjugations.

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Recombination in bacteria and in viruses that infect bacteria.

Four E. coli strains of genotype a+ b- are labeled 1,2,3 and 4. Four strains of genotype a- b+ are labeled 5,6,7, and 8. The two genotypes are mixed in all possible combinations and (after incubation) plated to determine the frequency of a+ b+ recombinants. The following results were obtained, where M = many recombinants, L = low numbers of recombinants, and O = no recombinants.


On the basis of these results, assign a sex type (either Hfr, F+, or F-) to each of the strains.

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