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A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats and birds, the arms of primates, the front flippers of whales, and the forelegs of four-legged vertebrates like horses and crocodilians are all derived from the same ancestral tetrapod structure.
The alleles on the homologous chromosomes may be different, resulting in different phenotypes of the same genes. This mixing of maternal and paternal traits is enhanced by crossing over during meiosis, wherein lengths of chromosomal arms and the DNA they contain within a homologous chromosome pair are exchanged with one another. [3]
Sequences are either homologous or not. [3] This involves that the term "percent homology" is a misnomer. [4] As with morphological and anatomical structures, sequence similarity might occur because of convergent evolution, or, as with shorter sequences, by chance, meaning
Homologous chromosomes, chromosomes in a biological cell that pair up (synapse) during meiosis; Homologous recombination, genetic recombination in which nucleotide sequences are exchanged between molecules of DNA; Homologous desensitization, a receptor decreases its response to a signalling molecule when that agonist is in high concentration
Functionally similar features that have arisen through convergent evolution are analogous, whereas homologous structures or traits have a common origin but can have dissimilar functions. Bird, bat, and pterosaur wings are analogous structures, but their forelimbs are homologous, sharing an ancestral state despite serving different functions.
The pseudoautosomal regions or PARs are homologous sequences of nucleotides found within the sex chromosomes of species with an XY [1] or ZW [2] mechanism of sex determination. The pseudoautosomal regions get their name because any genes within them (so far at least 29 have been found for humans) [3] are inherited just like any autosomal genes.
What makes these homologous similarities particularly suggestive of common ancestry in the case of cytochrome c, in addition to the fact that the phylogenies derived from them match other phylogenies very well, is the high degree of functional redundancy of the cytochrome c molecule.
Homologous behaviors can theoretically be of at least two different varieties. [1] As with homologous anatomical characteristics , behaviors present in different species can be considered homologous if they are likely present in those species because the behaviors were present in a common ancestor of the two species.