Anonymous asked in Science & MathematicsBiology · 2 months ago

Help with gene linkage and mapping!?

Attached is a question I've been trying to figure out. How's my reasoning?

My annotations are in red. So far, I've figured out:

We know 630 colonies survived when plated with ACD antibiotics...meaning they picked up the a/c/d resistance alleles, but remain wild-type for the b allele. Because SO MANY (630!) colonies seemed to inherit a/c/d together, and b completely separate from them, I would say b is the gene quite distant from the 3 other genes.

Now, to determine order of other 3 genes:

- 942 (many!!!) picked up A/D together. So A/D are probably adjacent.

- Then, 786 (many, but fewer) picked up C/D together. So C is further from D than A is far from D. The question becomes: is it "C---A-D" or is it "A-D---C"?

- Insight comes in with 640 (still fewer) picked up A/C together. That means A is quite FAR from C, because more distance = more recombination events that could split them up. So between the "C---A-D" or "A-D---C" listed above, it's more likely "A-D---C".

- We know B is far from the other ones, BUT is it like "B-------ADC", or is it like "ADC-------B"? Well, let's look: picked up B/C together is 51, but picked up A/B together is only 46. That means A is a little FURTHER from B than C is further from B, since 46 < 51.

- This led me to my proposed answer: that the order is "ADC---------B", or if you just flip it around, its equivalent: "B---------CDA".

How's my reasoning?

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1 Answer

  • 2 months ago

    You did not present the question and background information here exactly as it was presented to you.

    You did not quite ask a question.

    The question itself may be flawed. Typically you do linkage mapping with an Hfr strain, not through transformation.

    Bacteria have plasmids. Did you consider the possibility that A, C, and D are on the same plasmid and B is on a different plasmid?

    Consider this possibility too: B is being picked up much less than any of the others. Maybe B is part of the main chromosome and it's a big dragging chromosome and thus much less likely to be picked up than the much smaller plasmid that hosts A, C, and D.

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