Question

Resistance to antibiotics is conferred by (a) Plasmid DNA (b) Chromosome (c) Both (a) and (b) (d) None of these

Short answer

(c) Both (a) and (b)

Step-by-step solution

Understanding basic genetic concepts

Genes are sequences of DNA that determine the traits of an organism. In bacteria, genes can be located on the bacterial chromosome or on plasmids. Plasmids are small, circular pieces of DNA that are separate from the bacterial chromosome.

Recognizing bacterial resistance to antibiotics

Bacteria can become resistant to antibiotics through the acquisition of resistance genes. These genes can be located on either the bacterial chromosome or on plasmids. When these genes are located on plasmids, they can be easily transferred between bacteria, leading to the spread of antibiotic resistance.

Concluding the answer

Since antibiotic resistance can be conferred by genes located on either the chromosome or on plasmids in bacteria, the correct answer must be (c) Both (a) and (b).

Key concepts

Plasmid DNA

Plasmid DNA is a fascinating and crucial component of many bacterial cells. Plasmids are small, circular DNA molecules that exist independently of the chromosomal DNA within a cell. Despite their size, plasmids can carry genes that confer a significant advantage to the bacterium, such as antibiotic resistance.

One of the key features of plasmids is their ability to replicate independently of the bacterial chromosome. This means they can exist in many copies within a single cell, increasing the likelihood of passing on advantageous genes to offspring.

Plasmids often contain genes that are not necessary for the basic survival of the bacteria but can provide adaptations to various environmental challenges.

• Antibiotic resistance genes are a typical example of these adaptable traits found on plasmids.
• Such genes can rapidly spread among bacterial populations because plasmids can move from one bacterium to another through a process known as horizontal gene transfer.

This transferability makes plasmid DNA a potent vehicle for the spread of antibiotic resistance, creating significant challenges for public health.

Bacterial Chromosome

The bacterial chromosome is quite distinct from plasmid DNA. It is a long, continuous loop of double-stranded DNA that contains most of the genetic information necessary for the growth and reproduction of the bacterium. Unlike plasmid DNA, which is small and circular, the bacterial chromosome is much larger and essentially contains the core genetic blueprint of the bacterium.

Although the chromosome is the primary genetic information carrier, it can also harbor genes that contribute to antibiotic resistance. These genes typically arise through mutations or genetic exchanges that facilitate the survival of bacteria in antibiotic-rich environments.

• The integration of foreign genetic material into the chromosome can lead to stabilized resistance attributes in the bacterial population.
• Such genes may be less mobile than those on plasmids but are no less important for the study of resistance mechanisms.

Understanding the bacterial chromosome's role in antibiotic resistance is crucial for developing strategies to combat resistant strains.

Genetic Concepts

Genetic concepts form the backbone of understanding how traits such as antibiotic resistance develop and spread among bacterial populations. At the core of these concepts is the principle of gene transfer, crucial for bacterial adaptation and evolution. Understanding this principle helps explain how resistance traits can emerge quickly and become prevalent.

In bacteria, there are three primary methods of genetic exchange:

• Transformation, where bacteria pick up free DNA fragments from their surroundings.
• Conjugation, which involves direct DNA transfer between bacteria, often mediated by plasmids.
• Transduction, where bacterial viruses, or bacteriophages, ferry genetic material from one bacterium to another.

These processes facilitate the continuous mix and match of genetic material, allowing bacteria to develop resistance to antibiotics swiftly.

Grasping these genetic concepts is vital for future innovations in antibiotic therapy and for predicting the ways bacterial populations might respond to new antibiotics.