Cell Genes Hfr Tra Orit Transferred Recipient Allele

This hypothetical condition describes the mixing of one Hfr cell with 100 F– recipients. Over time, with no cell division occurring, one Hfr cell would repeatedly conjugate with the F– cells and transfer one strand of its chromosomal DNA in sequence, beginning with oriT and theoretically ending with the tra genes. 

The most frequently transferred bacterial genes also have the greatest likelihood of successful recombination (those closest to oriT, in this example, A allele). The entire chromosome is so large that it is virtually never transferred in its entirety and thus, the tra genes would not be transferred. (Even if tra genes were transferred, oriT and tra genes have no homologous regions in the recipient cell chromosome and would not successfully recombine within) Thus, the recipient cell acquires only new chromosomal alleles and NOT the whole fertility factor and never changes phenotype to become an Hfr cell. Therefore, any of the answers with cell one (the Hfr parent) as the dominant type would be wrong. The genes are transferred in linear order, so allele A will always be trans ferred more frequently than any of the later genes. 

Therefore, given sufficient time for conjugation, the cell type that would be most numerous is that of the recipient genotype with a newly acquired allele close to oriT. This means that the best answer is choice F: cell two with a new A gene. The farther from oriT that the allele is, the less likely that it will be successfully transferred. 

The distractor, choice C, with all 4 alleles transferred in, is less likely. 469