Question

Pili in bacteria represent
A. Extra chromosomal genetic element
B. Protoplasmic outgrowth of donor cells
C. Small flagella
D. Special bacterial cilia

Answer 1

Pili in the bacteria are the hair-like structure or appendage. It is available on the surface of the bacteria and archaea. It is used in bacterial conjugation. It is not used for motility and it is used for adhering to other bacteria or animal cells. Short attachment pili are known as the fimbriae. It is short and in numerous amounts. It is used to enable the bacteria to colonize in environmental surfaces of the cells and also it resists flushing.

Complete answer:
Option A: Extra chromosomal genetic elements are DNA and RNA. It has the ability to replicate the host chromosome independently. Plasmids are also called the extra chromosomal element. It is in a circular shape. Sometimes it may be linear. They occur in prokaryotes and eukaryotes, sometimes in the cytoplasm. Pili are not the extra chromosomal genetic element. Option A is incorrect.
Option B: Pili are the protoplasmic outgrowth of bacteria. It is used for the transformation of genetic material to other bacteria cells. Pili are used for conjugation. Conjugation is the process of transferring the DNA to another cell. It performs both import and export transformation of DNA. Option B is correct.
Option C: Flagella is available in the euglena. It is used for movement. It has a long whip like structure. Flagella are placed in the front of euglena and twirls to pull the cell through water. It is attached to a reservoir. Option C is incorrect.
Option D: Retinal photoreceptor cells possess the highly specialized primary cilia. It has two types. They are motile and non motile cilia. Non-motile cilia serve as sensory organelles. Option D is incorrect.

Therefore, Option B is the correct answer.

Note:
In bacteria, plasmid is the extra chromosomal genetic element. It is very small compared to the bacterial chromosome. Pili have two types. They are short attachment pill and long conjugation pili. It occurs in gram-negative bacteria. It is made of pilin protein. It is longer and thicker. One to ten pili occurs in one bacterial cell. Pili is non helical and straight. It comes from the cytoplasmic membrane. It has conjugation and type four pili.