The sexual nature of the eukaryote genome

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Updated: Nov 1, 2026

Microscopy of Fission Yeast Sexual Lifecycle
07:47

Microscopy of Fission Yeast Sexual Lifecycle

Published on: March 9, 2016

G Bell1

  • 1Biology Department, McGill University, Montreal, Quebec, Canada.

The Journal of Heredity
|September 1, 1993
PubMed

Insights

The sexual cycle in eukaryotes likely originated from genome parasites infecting cells. These parasites facilitated gene transfer and evolved into key components of eukaryotic reproduction and genome organization.

Area of Science:

  • Evolutionary Biology
  • Genetics
  • Molecular Biology

Background:

  • Conjugative plasmids in prokaryotes facilitate gene transfer via cell fusion.
  • Gene transfer mechanisms exist between prokaryotes and eukaryotes, with plasmid integration into eukaryotic genomes.
  • Eukaryotic genomes exhibit gene transfer between unrelated species and within cells.

Purpose of the Study:

  • To support the conjecture that eukaryotic sexual cycles originated from genome parasite infections.
  • To explore the parasitic origins of key eukaryotic reproductive and genomic elements.

Main Methods:

  • Comparative analysis of gene transfer mechanisms in prokaryotes and eukaryotes.
  • Examination of mobile genetic elements (transposons, retroviruses) and their relationship to eukaryotic sexual systems.
  • Analysis of mating-type genes (idiomorphs) in fungi and their proposed parasitic origin.

Main Results:

  • Conjugative plasmids enable gene transfer and integration into eukaryotic genomes.
  • Transposons and retroviruses act as parasites of the eukaryotic sexual system.
  • Mating-type idiomorphs in fungi are proposed to be integrated parasitic elements driving cell fusion, with variations reflecting independent acquisitions.
  • Sexual competence loss is common, and novel mating-type alleles spread parasitically.
  • Centromeres may have evolved for plasmid persistence, and crossing over favors gene unlinking from inferior genomes.

Conclusions:

  • The eukaryotic sexual cycle likely arose from the integration of genome parasites.
  • Parasitic elements have shaped key aspects of eukaryotic reproduction, including mating-type determination and genome organization.
  • Mobile genetic elements and their interactions provide insights into the evolutionary origins of eukaryotic complexity.

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