Sequence homology
Sequence Homology
Sequence homology (/sɪˈkwɛns hoʊˈmɒlədʒi/) is a concept in molecular biology that refers to the similarity in the nucleotide sequence of DNA or RNA molecules, or the amino acid sequence of proteins.
Etymology
The term "homology" originates from the Greek words "homos" meaning "same" and "logos" meaning "relation". In the context of sequence homology, it refers to the evolutionary relationship between sequences derived from a common ancestor.
Types of Sequence Homology
There are three main types of sequence homology:
- Orthologous sequences: These are sequences in different species that have evolved from a common ancestral gene by speciation. Usually, orthologous genes retain the same function in the course of evolution.
- Paralogous sequences: These are sequences that are related by gene duplication within a genome. Paralogous genes often evolve new functions, even if these are related to the original one.
- Xenologous sequences: These are sequences that are related by horizontal gene transfer.
Related Terms
- Homologous recombination: A type of genetic recombination in which nucleotide sequences are exchanged between two similar or identical molecules of DNA.
- Homologous chromosome: A pair of the same length, centromere position, and staining pattern, for genes with the same corresponding loci.
- Homologous gene: Genes derived from the same ancestral gene that have evolved to perform slightly different tasks.
See Also
External links
- Medical encyclopedia article on Sequence homology
- Wikipedia's article - Sequence homology
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