Why are the recombinants produced from an hfr x f- cross rarely, if ever, f+?

The F factor straightly handover the donor chromosome in the cross. H takes roughly 90 minutes to transfer the chromosome. The big share of the F factor is last to be transmitted and the conjugation tube is very subtle so the probability for a thorough transfer is low. Consequently, when the bacterial strain attempts to inoculate an Hfr plasmid into an F- strain transversely the conjugation bridge through rolling circle replication, it is infrequently completed and typically breakdowns off before the F factor section is totally transferred. 

The correct answer is b

The virus is considered to be are living item since they have hereditary material dnas or rnas. they can imitate and change. they respond to boosts, for example, radiation, chemicals, and warmth. they have antigenic properties. they are proficient to duplicate with a same hereditary constituent.