1.The function of six hypothetical genes in a microbial organism are shown below
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Question
1.The function of six hypothetical genes in a microbial organism are shown below:
Gene Function of the type of gene
GRA Required for the utilization of the sugar granulose as a carbon source
RAC Required for sensitivity to the drug ractocine
IOB Required for the synthesis of the vitamin iobine
YYZ Required for resistance to YYZ virus
PET Required for the synthesis of the growth hormone petozone
AOA Required for the growth of hyphae from the cell
Based on the function of these genes suggest one possible genetic screen to identify a loss-of-function mutation in each of these genes.
2. You construct the following genetic map distances between these genes
Gene GRA RAC IOB YYZ PET AOA
GRA _ 2.5 0.1 1.9 0.7 2.0
RAC 2.5 _ 2.6 0.6 3.2 0.5
IOB 0.1 2.6 _ 2.0 0.6 2.1
YYZ 1.9 0.6 2.0 _ 2.6 0.1
PET 0.7 3.2 0.6 2.6 _ 2.7
AOA 2.0 0.5 2.1 0.1 2.7 _
Base on these map distances construct a genetic map that includes all of these genes.
3. You decide to revert the iob- mutant to wild type (IOB+) using different mutagens and find the following reversion rates for each mutagen tested
Mutagen Rate of reversion to IOB+ (%)
2-aminopurine 98
5-bromouracil 95
Nitrous acid 94
Proflavin 2
Spontaneous 4
What is the most likely molecular basis of the original iob- mutation?
What does this reversion test data suggest about the most prominent mechanism of spontaneous mutations in this organism?
4.You decide to isolate deletion mutations in the IOB gene. Suggest a genetic screen that would enrich for deletion mutations in this gene over other types of loss-of-function mutations.
5. Suggest two genetic tests that would show you have indeed identified iob deletion mutants?
6. It is generally understood that deletion a gene result in a null phenotype for that gene function. Assuming you have a deletion of IOB gene you now want to determine if the original iob loss-of-function mutant you identified in Question 1 is a true null mutant. How can you use the deletion mutant you found in Question 4 to do this?
Explanation / Answer
1.) GRA: put organisms in a medium with sugar granulose as the only carbon source RAC: IOB: test for the organisms with iobine YYZ: introduce YYZ virus PET: test for growth hormone AOA: test for hyphae
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