Question

Which of the following statements about plasmids is incorrect?

• A. Plasmids have the ability to replicate within the bacterial cell.
• B. Their replication is controlled by chromosomal DNA.
• C. They are autonomously replicating circular extra-chromosomal DNA.
• D. They often carry antibiotic resistant genes.

Hint:

Plasmids are "autonomous," which is the scientific word for "self-governing" or "independent" regarding replication.

Answer 1

The Correct Option is B

To determine which statement about plasmids is incorrect, let's evaluate each of the given statements.

1. Plasmids have the ability to replicate within the bacterial cell. 
   This statement is correct. Plasmids are small, circular pieces of DNA found in bacteria separate from the chromosomal DNA. They have their own origin of replication, which allows them to replicate independently within the bacterial cell.
2. Their replication is controlled by chromosomal DNA. 
   This statement is incorrect. Plasmids are known for their ability to replicate autonomously. This means that their replication is not directly controlled by the chromosomal DNA of the host cell but by their own genetic material.
3. They are autonomously replicating circular extra-chromosomal DNA. 
   This statement is correct. Plasmids exist outside the chromosomal DNA in bacteria and can replicate on their own, which is a defining feature of plasmids.
4. They often carry antibiotic resistant genes. 
   This statement is correct. One of the significant roles of plasmids is to carry genes that confer advantages to bacteria, such as antibiotic resistance, which can be shared between bacteria through horizontal gene transfer.

Thus, the incorrect statement is that the replication of plasmids is controlled by chromosomal DNA.