Question

Sex factor in bacteria is
A. F-pilus
B. Chromosomal replicon
C. RNA
D. None of the above.

Answer 1

It is one of the characteristic of Escherichia coli carrying the conjugative plasmid F. They belong to the class of Gram-negative thin, flexible filaments that function in horizontal gene transport.

Complete answer:
To answer this question, first, we need to know about sex factor in bacteria. The fertility factor is called the sex factor in E. coli allows genes to be carried from one bacterium carrying the factor to another bacterium lacking the factor by conjugation. The F factor was the first plasmid to be recognized. Not similar with other plasmids, F factor is constitutive for transfer proteins due to a mutation in the gene finO. The F plasmid belongs to a class of conjugative plasmids that control sexual functions of bacteria with a fertility inhibition (Fin) system.
Now, let us find the solution from the option.
The bacterial cells are of two types, F+ and F−. The F+ cell possesses a circular plasmid containing the gene called as the sex factor. This sex factor is responsible for the growth of F-pili which is involved in the process of conjugation where the lateral transfer of genes takes place.

The replicon is the whole chromosome. Plasmids and bacteriophages are commonly divided as single replicons, but big plasmids in Gram-negative bacteria have been displayed to transfer several replicons.

Bacterial small RNAs (sRNA) are tiny RNAs formed by bacteria; they range from 50 to 500 nucleotide non-coding RNA molecules, extremely structured and consisting of several stem-loops.

Thus, the correct option is A. i.e. F-pilus.

Note: Sometimes the F factor may become combined with the chromosome of an F+ bacterium to form a high-frequency recombinant (Hfr) cell. This allows the part of the host chromosome nearest to the F factor to be carried to the recipient by conjugation.