Which of the following is not true for plasmids? They are circular DNA molecules that replicate independently of bacterial chromosome Plasmids often carry antibiotic resistance genes Many DNA sequences in bacteria are mobile and transferable Plasmids are used in genetic engineering They are double stranded RNA molecules
The Correct Answer and Explanation is:
The statement that “Plasmids are double stranded RNA molecules” is not true.
Explanation:
Plasmids are circular DNA molecules, not RNA. They are found in many bacteria, as well as some archaea, and they replicate independently of the bacterial chromosome. These small, extrachromosomal DNA molecules typically carry genes that provide an advantage to the bacteria, such as antibiotic resistance genes. This gives bacteria a survival edge in hostile environments, particularly in the presence of antibiotics.
Here’s a breakdown of the other statements:
- “Plasmids are circular DNA molecules that replicate independently of bacterial chromosome”: This is true. Plasmids are small, circular pieces of DNA that exist outside the bacterial chromosome and can replicate independently. They are a form of extrachromosomal DNA.
- “Plasmids often carry antibiotic resistance genes”: This is true. One of the most important functions of plasmids is to carry genes that confer resistance to antibiotics. These resistance genes are often transferred between bacteria, a process that contributes to the spread of antibiotic resistance.
- “Many DNA sequences in bacteria are mobile and transferable”: This is true. Many bacterial DNA sequences, including plasmids, can be transferred between bacteria. This can occur through horizontal gene transfer mechanisms like conjugation, transformation, and transduction. This mobility allows genetic traits, such as antibiotic resistance, to spread rapidly in bacterial populations.
- “Plasmids are used in genetic engineering”: This is true. Plasmids are widely used in molecular biology and genetic engineering to clone, transfer, and express genes. Scientists can insert a gene of interest into a plasmid and introduce it into a host cell, such as bacteria, to produce the gene product or study gene function.
In conclusion, the key misconception here is the idea that plasmids are made of RNA. They are actually double-stranded DNA molecules, crucial to many bacterial processes, including antibiotic resistance and gene transfer.
