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Related Concept Videos

Nucleoid01:24

Nucleoid

The nucleoid represents a structurally and functionally distinct region within prokaryotic cells, where the cell's DNA and associated proteins are housed. Unlike eukaryotic cells, prokaryotes lack a membrane-bound nucleus, and the nucleoid facilitates the organization and accessibility of the genetic material within this constraint. The DNA in most bacteria and archaea exists as a single, circular, double-stranded molecule that is highly compacted through supercoiling and interactions with...
The Nucleus01:32

The Nucleus

The nucleus is a membrane-bound organelle that acts as a control center in a eukaryotic cell. It contains chromosomal DNA, which controls gene expression and precisely regulates the production of proteins within the cell. In contrast, the DNA inside the mitochondria and chloroplast only carries out functions that are specific to those organelles.
Arrangement of DNA within Nucleus
The regulation of gene expression inside the nucleus is dependent on many factors, including the DNA structure. The...
The Nucleus01:25

The Nucleus

The nucleus is a membrane-bound organelle that acts as a control center in a eukaryotic cell. It contains chromosomal DNA, which controls gene expression and precisely regulates the production of proteins within the cell. In contrast, the DNA inside the mitochondria and chloroplast only carries out functions that are specific to those organelles.
Arrangement of DNA within Nucleus
The regulation of gene expression inside the nucleus is dependent on many factors, including the DNA structure. The...
The Nucleus01:25

The Nucleus

The nucleus is a membrane-bound organelle that acts as a control center in a eukaryotic cell. It contains chromosomal DNA, which controls gene expression and precisely regulates the production of proteins within the cell. In contrast, the DNA inside the mitochondria and chloroplast only carries out functions that are specific to those organelles.
Arrangement of DNA within Nucleus
The regulation of gene expression inside the nucleus is dependent on many factors, including the DNA structure. The...
The Nucleolus02:55

The Nucleolus

The nucleolus is the most prominent substructure of the nucleus. When it was first discovered, it was considered to be an isolated organelle that forms fibrils and granules. In 1931, the relationship between the nucleolus and chromosomes was first described by Heitz. He observed that the appearance and size of nucleolus varies depending on the stage of the cell cycle. He also noticed constricted regions on different chromosomes clustered together at definite cell cycle stages. These regions,...
The Nucleolus02:55

The Nucleolus

The nucleolus is the most prominent substructure of the nucleus. When it was first discovered, it was considered to be an isolated organelle that forms fibrils and granules. In 1931, the relationship between the nucleolus and chromosomes was first described by Heitz. He observed that the appearance and size of nucleolus varies depending on the stage of the cell cycle. He also noticed constricted regions on different chromosomes clustered together at definite cell cycle stages. These regions,...

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Specific Labeling of Mitochondrial Nucleoids for Time-lapse Structured Illumination Microscopy
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Specific Labeling of Mitochondrial Nucleoids for Time-lapse Structured Illumination Microscopy

Published on: June 4, 2020

Nucleomorph genomes.

Christa E Moore1, John M Archibald

  • 1The Canadian Institute for Advanced Research, Program in Integrated Microbial Biodiversity, Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, B3H 1X5, Canada.

Annual Review of Genetics
|August 19, 2009
PubMed
Summary
This summary is machine-generated.

Nucleomorphs, remnant nuclei from algal endosymbionts in cryptophytes and chlorarachniophytes, exhibit highly reduced genomes. Their convergent evolution offers insights into genome reduction in eukaryotic lineages.

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Area of Science:

  • Eukaryotic genomics
  • Evolutionary biology
  • Algal endosymbiosis

Background:

  • Nucleomorphs are vestigial nuclei from secondary endosymbiotic events in cryptophyte and chlorarachniophyte algae.
  • These algae engulfed red and green algae, respectively, retaining their nuclei as nucleomorphs.
  • Nucleomorph genomes are exceptionally small (<1 Mbp) with prokaryotic gene density.

Purpose of the Study:

  • To review the current understanding of nucleomorph structure, function, origin, and evolution.
  • To explore the convergent evolution of genome architecture and coding capacity in independent nucleomorph lineages.
  • To highlight nucleomorphs as a model for studying reductive genome evolution.

Main Methods:

  • Literature review of existing studies on cryptophyte and chlorarachniophyte nucleomorphs.
  • Comparative analysis of nucleomorph genome structures and gene content.
  • Synthesis of data on evolutionary trajectories and selective pressures.

Main Results:

  • Nucleomorph genomes are among the most reduced known, featuring three small linear chromosomes.
  • Independent origins in cryptophytes and chlorarachniophytes led to striking convergence in genome architecture.
  • Prokaryote-like gene density is observed despite eukaryotic origin.

Conclusions:

  • Nucleomorphs provide a unique system for studying the mechanisms and outcomes of genome reduction.
  • Convergent evolution in nucleomorphs underscores the power of selective forces in shaping genome size and organization.
  • Further research into cryptophyte and chlorarachniophyte diversity will illuminate the evolutionary pathways of these enigmatic genomes.