Question

Read the statements below and answer the question.

At time zero, an Hfr strain (strain 1) was mixed with an F' strain and various times after mixing, samples were removed and agitated to separate conjugating cells. The cross may be written as Hfr 1:$a^{-}{b}^{-}{c}^{-}{d}^{-}{e}^{-}{f}^{-}{g}^{-}{h}^{-}St{r}^R$, no order is implied in the above listing. The samples were then plated onto a selective media to measure the frequency of $hSt{r}^R$ recombinants that had received certain genes from the Hfr cell. The following graph shows the percentage of recombinants against time in minutes.

Hfr strain stands for

• A. Haematoxylin fast reaction
• B. High frequency recombination cells
• C. High female reactive cells
• D. High female recombination cells

Answer 1

The correct option is B High frequency recombination cells

A F${}^{+}$ strain is characterized by presence of fertility factor that make the bacteria donor in a recombination process. The recombination frequency for F factor is independent and higher than that of chromosomal genes. Hfr stands for high frequencyrecombinants that show high recombination frequency of both chromosomal genes as well as F factor. Correct answer is option B.