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Related Concept Videos

Convergent Evolution01:54

Convergent Evolution

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Evolution shapes the features of organisms over time, ensuring that they are suited for the environments in which they live. Sometimes, selection pressure leads to the rise of similar but unrelated adaptations in organisms with no recent common ancestors, a process known as convergent evolution.
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Gene Duplication and Divergence02:37

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The seminal work of Ohno in 1970 popularized the idea of gene duplication and divergence. DNA sequence comparison studies reveal that a large portion of the genes in bacteria, archaebacteria, and eukaryotes was  generated by gene duplication and divergence, indicating its critical role in evolution.
The duplicated copies of the gene are called Paralogs. Paralogs with similar sequences and functions form a gene family. Across several species, a large number of gene families are...
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When cells are placed in a hypotonic (low-salt) fluid, they can swell and burst. Meanwhile, cells in a hypertonic solution—with a higher salt concentration—can shrivel and die. How do fish cells avoid these gruesome fates in hypotonic freshwater or hypertonic seawater environments?
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Complement System01:27

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The complement system is a group of approximately 20 plasma proteins that strengthen the body's defenses against infections through opsonization, inflammation, and cell lysis. Opsonization involves coating pathogens with complement proteins, making them more recognizable and facilitating phagocyte engulfment. Certain complement proteins induce inflammation that attracts immune cells to the site of infection. Cell lysis involves the destruction of pathogens through the formation of a...
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Groups of proteins may form a complex where each protein in this complex has a different role in the overall execution of the complex’s function. Often some of the proteins in the complex can be replaced by a closely related variant to give a complex that contains many of the same components yet is functionally distinct.
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The evolution of new genes is critical for speciation. Exon recombination, also known as exon shuffling or domain shuffling, is an important means of new gene formation. It is observed across vertebrates, invertebrates, and in some plants such as potatoes and sunflowers. During exon recombination, exons from the same or different genes recombine and produce new exon-intron combinations, which might evolve into new genes. 
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Related Experiment Video

Updated: Nov 13, 2025

Dissection and Flat-mounting of the Threespine Stickleback Branchial Skeleton
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Dissection and Flat-mounting of the Threespine Stickleback Branchial Skeleton

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Tracing and exploring the evolutionary origin and systematic function of fish complement C9.

Lisen Li1, Yubang Shen2, Xiaoyan Xu1

  • 1Key Laboratory of Freshwater Aquatic Genetic Resources, Ministry of Agriculture and Rural Affairs, College of Aquaculture and Life Science, Shanghai Ocean University, Shanghai, 201306, China.

Molecular Genetics and Genomics : MGG
|March 15, 2021
PubMed
Summary
This summary is machine-generated.

Complement C9 (terminal complement component) shows significant evolutionary divergence. Its gene structure and function differ between fish and higher vertebrates, impacting innate immunity.

Keywords:
Complement C9Gene elementImmunityPathway analysis

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Manipulation of Gene Function in Mexican Cavefish
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Area of Science:

  • Immunology
  • Evolutionary Biology
  • Molecular Biology

Background:

  • Complement C9 is a key component of the terminal complement system, crucial for innate immunity.
  • Evolutionary differences in complement components exist between lower and higher vertebrates, necessitating further study.

Purpose of the Study:

  • To investigate the evolutionary origin and systematic function of complement C9 in fish and non-fish vertebrates.
  • To explore complement gene evolution and potential functions in fish using molecular and structural biology.

Main Methods:

  • Comparative analysis of C9 gene sequences and optimal codons across vertebrate groups.
  • Identification of conserved amino acids in the C9 TMH1 region.
  • Gene/protein regulatory network and pathway analyses.

Main Results:

  • Complete divergence of C9 observed throughout gene evolution, with optimal codons favoring lower vertebrates.
  • Conserved amino acids in the C9 TMH1 region suggest roles in MAC formation and pore generation.
  • Differential distribution of transposons and repeats highlights regulatory complexity in higher vertebrates.

Conclusions:

  • Complement C9 exhibits significant evolutionary divergence, with distinct systematic functions across species.
  • Negative selection pressures enhance sequence conservation in fish and non-fish groups.
  • Altered protein conformation in higher vertebrates suggests more complex C9 functions, offering insights into complement evolution.