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Old 08-10-2012
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Bacteria Bacterial Genetic Recombination (HFR Donor)

The table below lists the observed frequency of the appearance of wild-type recombinations for four gene markers using an Hfr donor strain.

Marker Frequency in F– Recipient
His+ --------Lac+---------- Ilv+-------- Arg+
5.0%-------- 30.0% --------80.0%------ 0.03%

Which of the following provides the correct location and direction of transfer of genes in the Hfr bacterial chromosome?

A) The F factor has integrated between Arg and Ilv with Ilv transferred first

B) The F factor has integrated between His and Arg with Arg transferred first

C) The F factor has integrated between His and Arg with His transferred first

D) The F factor has integrated between Ilv and Lac with Ilv transferred first

E) The F factor has integrated between Ilv and Lac with Lac transferred first
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Old 08-11-2012
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I think the answer is A, because Ilv marker shows the highest recombination frequency and the Arg the lowest.
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Old 08-11-2012
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Default the key is the percentages, then draw a circle.

The answer is A.

In Hfr conjugation, the whole chromosome attempts to transfer. But this is usually not completed. The genes at the start point get transferred first and they will be reflected most in the progeny.

First step in answering this question is to note the percentages. This tells you who is transferred first (the largest percentage).

Then draw a circle, the gene transferred first and the one transferred last will sit adjacent to each other.
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Old 08-11-2012
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Agree with you two. Should be A.
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