Microbial Evolution and Systematics - The Evolution of Microbial Genomes

11 important questions on Microbial Evolution and Systematics - The Evolution of Microbial Genomes

What is the difference between microbial evolution and eucaryotic evolution?

- Horizontal Gene transfer
- Asexual reproduction
- Haploid (Prokaryotes are always haploid).

How does evolution modify a microbe's genome over long time periods?

Evolution modifies a microbe's genome over long time periods through mutations and genetic recombination.

What are some aspects of microbial evolution that are uncommon in plants and animals?

Some uncommon aspects of microbial evolution include the haploid and asexual nature of Bacteria and Archaea, mechanisms for horizontal gene transfer, and highly heterogeneous and dynamic genomes.
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What is the simplest form of evolution, and how is it defined?

In its simplest form, evolution is a change in allele frequencies in a population of organisms over time, resulting in descent with modification. Alleles are alternate versions of a given gene.

What are the fundamental sources of natural variation that drive the evolutionary process?

Mutations, which are random changes in DNA sequence that accumulate over time, are fundamental sources of natural variation. Recombination, a process by which segments of DNA are broken and rejoined to create new combinations of genetic material, also contributes to natural variation.

How do gene duplication events contribute to the diversification of gene function?

Gene duplication events produce a redundant copy of a gene that can be modified by further mutation without losing the function encoded by the original gene. This allows for the diversification of gene function.

What is genetic drift, and how does it contribute to evolution?

Genetic drift is a random process that can cause gene frequencies to change over time, resulting in evolution in the absence of natural selection. It occurs because some members of a population will have more offspring than others simply as a result of chance.

Why are deleterious mutations generally purged from populations over time?

Deleterious mutations decrease the fitness of an organism by disrupting gene function. These mutations are generally purged from populations over time by natural selection.

How does the selective nature of the environment influence adaptive mutations?

The selective nature of the environment does not cause adaptive mutations but simply selects for the growth and reproduction of those organisms that have incurred mutations that provide a fitness advantage.

What is the molecular clock, and how is it used in estimating the time of divergence between microbial species?

The molecular clock is a method that uses nucleotide changes in gene sequences to estimate the time since a species has diverged from its closest relatives. It assumes that nucleotide changes accumulate in a sequence in proportion to time, are generally neutral, and are random.

Provide an example of microbial speciation based on molecular clock estimates.

Molecular clock estimates indicate that the closely related species Escherichia coli and Salmonella enterica (typhimurium), which have 2.8% dissimilarity in their 16S rRNA gene sequences, last shared a common ancestor some 100–140 million years ago.

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