In a transduction experiment where the recipient is Met-, Ala-, Gal- you observe a recombinant phenotype Met+, Gal+ in some strains and Gal+ Ala+ in some strains. But in none of the cases can you find Met+ Ala+. What is the sequence of the gene?
A. Met, Ala, Gal
B. Met, Gal, Ala
C. Gal, Met, Ala
D. Gal, Ala, Met
Answer:B
In a transduction experiment where the recipient is Met-, Ala-, Gal- you observe a recombinant phenotype Met+, Gal+ in some strains and Gal+ Ala+ in some strains. But in none of the cases can you find Met+ Ala+. What is the sequence of the gene?
A. Met, Ala, Gal B. Met, Gal, Ala C. Gal, Met, Ala D. Gal, Ala, Met
Explanation: The recombinant genotype Met+ Ala+ will only result in the case when there is a double cross over such that the middle portion is exchanged twice. This is of least occurrence and is deterministic for the sequence.