Question

Genetic diversity is maintained in bacterial populations by all of the following except a. binary fission. d. transduction. b. mutation. e. conjugation. c. transformation.

Short answer

Binary fission does not maintain genetic diversity among bacterial populations.

Step-by-step solution

Understanding Genetic Mechanisms

Bacteria can pass genetic material in several ways. Conjugation is a process in which one bacterium transfers DNA to another bacterium. Transformation involves bacteria absorbing foreign DNA from their environment. Transduction is when a bacteriophage (a virus that infects bacteria) carries bacterial DNA from one bacterium to another. Mutation refers to changes in the DNA sequence of a bacterium. Binary fission is the process by which a bacterium replicates its DNA and divides in two, creating two identical daughter cells.

Assessing Genetic Diversity

All the processes above, except binary fission, introduce variation and therefore contribute to genetic diversity. Mutation creates new genes or alters existing ones, leading to new genetic variants. Conjugation, transformation, and transduction allow for the exchange of different genes between bacteria, contributing to genetic diversity. In contrast, binary fission does not provide any new genetic material or genetic variation.

Key concepts

Binary Fission

Binary fission is the primary method by which bacteria reproduce. It is a straightforward and efficient process that allows bacteria to make identical copies of themselves. During binary fission, a single bacterial cell duplicates its genetic material—its DNA. This is followed by the division of the cell into two separate, but identical, daughter cells.

Since binary fission produces clones of the original bacterium, it does not contribute to genetic diversity within a bacterial population. Each new cell is genetically identical to its parent cell, therefore there is no variability introduced through this process.

The advantage of binary fission lies in its speed, which allows for rapid population growth. However, because all offspring are genetic clones, this can make bacterial populations vulnerable to changing environments where genetic variation would be required to survive new challenges.

Conjugation

Conjugation is a fascinating and important process in which one bacterium transfers genetic material to another through direct contact. This process often involves the formation of a structure known as a 'pilus', which connects two bacterial cells. Once connected, a copy of plasmid DNA (a small, circular piece of DNA distinct from the chromosomal DNA) is transferred from the donor to the recipient cell.

This transfer of DNA brings about genetic diversity in bacterial populations. As different combinations of genes are exchanged between bacteria, new genetic traits can emerge. This becomes especially significant in the spread of antibiotic resistance, as genes responsible for such traits can be shared through conjugation.

Conjugation does not require similar species to interact, which means it can potentially occur between different bacterial species. This ability increases the genetic diversity significantly within bacterial communities.

Transformation

Transformation is another mechanism that adds genetic variety to bacteria. In this process, bacterial cells take up free DNA fragments from their environment. This DNA is often released into the environment by other bacterial cells upon their death.

Once a bacterium integrates this foreign DNA into its own genome, it can acquire new genetic traits. The genetic changes brought about by transformation can lead to increased adaptability in fluctuating environments. It enables bacteria to make use of beneficial traits from other species, contributing to the genetic diversity.

This process has been observed in nature but is also an integral part of genetic engineering techniques used in laboratories, highlighting its practical significance in both natural and controlled environments.

Transduction

Transduction is a unique process mediated by viruses known as bacteriophages (or phages), which can transfer DNA from one bacterium to another. During a bacteriophage infection, these viruses can accidentally incorporate bacterial DNA into their viral genome.

When the phage infects another bacterial cell, it can introduce this acquired DNA into the new host. This can result in the exchange of genetic material between bacteria that are otherwise not directly interacting with each other. Such gene flow enhances genetic variability and can accelerate evolutionary changes in bacterial populations.

Transduction allows bacteria to share advantageous genes across distances, making it an important mechanism for spreading traits such as virulence factors or antibiotic resistance.

Mutation

Mutation is the process where changes occur in the DNA sequence of an organism. For bacteria, mutations can arise due to various factors such as errors during DNA replication, exposure to radiation, or interaction with mutagenic chemicals.

These changes are essential for introducing new genetic information into a bacterial population. Mutations can result in new traits, sometimes advantageous and sometimes detrimental. They are a driving force of evolution, offering new possibilities for adaptation to challenging environments.

Unlike other mechanisms like transformation or conjugation, mutations arise within a single organism without the need for external genetic exchange. However, once a beneficial mutation appears, it can rapidly spread through the population, especially when linked with other processes like conjugation or transduction.