Next-Gen

REDUCTIVE EVOLUTION OF GENOMES

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by mariaulloavallejo
Last updated 2 months ago

Discipline:
Science
Subject:
Evolutionary Biology
Grade:
12

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REDUCTIVE EVOLUTION OF GENOMES

REDUCTIVE EVOLUTION OF GENOMESSarai Araujo Aris, María Ulloa Vallejo

Evolution of life has always been described as a rise towards organismal complexity, in which the resulted genomes are far more elaborate than the original ones. However, although there are many evidences for an increase in genome complexity, some species evolve with simplification instead of complexification.

C-value paradox:The amount of DNA contained within an haploid nucleus. This paradox postulates that genome size does not reflect gene number in eukaryotes, since most of their DNA is non-coding and therefore does not consist of genes.

GENOME REDUCTIONGenome reduction or genome degradation is the process by which a genome shrinks relative to its ancestor. It produces the maintenance of the genes that are vital for this kind of organisms, removing the other ones.

Intracellular bacteria and intracellular pathogenic parasites.

MULLER'S RATCHET

ADAPTATIVE GENOME REDUCTION

Some non-synonymous substitutions have a deleterious effect on fitness. Most species:- Sexual reproduction, variability increased by recombination.- Big population sizes.Resident genomes of intracellular organisms:- Asexual, recombination is absent or very infrequent.- Small population sizes. - Often subjected to bottlenecks.

Robustness: The ability to code for functional protein products in frequently hard and variable environments.Highly required for free-living organisms.Predictable environments (intracellular lifestyle): Genome reduction under these conditions is believed to be associated with adaptation to a new lifestyle where many molecules can be obtained from the host.


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