Related Experiment Video
Updated: Oct 11, 2025
07:55
Detection of Homologous Recombination Intermediates via Proximity Ligation and Quantitative PCR in Saccharomyces cerevisiae
Published on: September 11, 2022
2.0K
On homology.
Kevin C Nixon1, James M Carpenter2
1Bailey Hortorium, Cornell University, Ithaca, NY 14853, USA.
Cladistics : the International Journal of the Willi Hennig Society
|December 4, 2021
Summary
This review clarifies homology in cladistics, distinguishing it from synapomorphy. It proposes a comprehensive definition encompassing various homology types for better phylogenetic analysis.
Area of Science:
- Systematic Biology
- Evolutionary Biology
- Phylogenetics
Background:
- The concept of homology is central to cladistics and understanding evolutionary relationships.
- Historical definitions and interpretations of homology have varied, necessitating a clear explication.
- Willi Hennig's work included both plesiomorphy and synapomorphy as types of homology.
Discussion:
- Homology is distinct from synapomorphy; it encompasses symplesiomorphy as well.
- Homoplasy is conceptualized as coding error, analogous to residual error in statistical regression.
- Distinguishing parallelism (homoplasy) from convergence (analogy) is discussed.
- Various forms of homology, including molecular, morphological, character state, nested, and serial homology, are examined.
Key Insights:
- Homology is not equivalent to synapomorphy and includes symplesiomorphy.
- Homoplasy represents error in character coding, not a direct evolutionary event.
- A unified, global definition of homology is proposed, integrating diverse interpretations.
Outlook:
- The proposed global definition aims to standardize homology assessment in cladistics.
- Clarifying homology enhances the accuracy of phylogenetic tree construction.
- Further research may explore the application of this definition across different biological systems.
Related Concept Videos
02:31Homologous Recombination
5.1K
5.1K
01:57Gene Families
9.3K
Gene families consist of groups of genes proposed to have originated from a common ancestor. Typically these arise through events in which a gene or genes are mistakenly duplicated during cell division. Unlike their parent genes (which are subject to selection pressure to maintain function), these gene copies do not need to preserve their sequences and may evolve at a relatively faster rate.
Occasionally these regions can be adapted to take on new roles within the organism, becoming novel genes...
Occasionally these regions can be adapted to take on new roles within the organism, becoming novel genes...
9.3K
01:54Convergent Evolution
29.5K
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.
29.5K
01:03¹H NMR Chemical Shift Equivalence: Homotopic and Heterotopic Protons
2.6K
Protons in identical electronic environments within a molecule are chemically equivalent and have the same chemical shift. The replacement test is a useful tool to identify chemical equivalence and predict NMR spectra. A substituent replaces each of the protons being examined and the resulting molecules are compared. If the same molecule is obtained, the protons are equivalent or homotopic. Replacement of any hydrogens in ethane by chlorine yields chloroethane because all six protons are...
2.6K
02:47Protein Families
16.1K
Protein families are groups of homologous proteins; that is, they have similarities in amino acid sequences and three-dimensional structures. Protein families usually occur because of gene duplication, where an additional copy of a gene is inserted into the genome of an organism. Mutations that change the amino acids but still allow the protein to be properly synthesized, will lead to new protein family members. If these new proteins contain similar amino acids in key...
16.1K
02:37Gene Duplication and Divergence
6.8K
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...
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...
6.8K