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Homologous sequences are paralogous if they were created by a duplication event within the genome. For gene duplication events, if a gene in an organism is duplicated, the two copies are paralogous. They can shape the structure of whole genomes and thus explain genome evolution to a large extent. Examples include the Homeobox genes in animals.
Diagrams that show the development of male and female organs from a common precursor. Sperm ducts and fallopian tubes are not homologous, as the sperm ducts originate from the Wolffian ducts, whereas the fallopian tubes originate from the Müllerian ducts. Homologous structures in the external genitalia
All vertebrate forelimbs are homologous, meaning that they all evolved from the same structures. For example, the flipper of a turtle or of a dolphin , the arm of a human, the foreleg of a horse, and the wings of both bats and birds are ultimately homologous, despite the large differences between them.
A drawing by Edward Tyson. Two major concepts of comparative anatomy are: Homologous structures - structures (body parts/anatomy) which are similar in different species because the species have common descent and have evolved, usually divergently, from a shared ancestor. They may or may not perform the same function.
When structures in different species are believed to exist and develop as a result of common, inherited genetic pathways, those structures are termed homologous. For example, the leaves of pine, oak, and cabbage all look very different, but share certain basic structures and arrangement of parts.
In the horizontal direction, the structures are homologous in their morphology, or anatomy, but different in their function due to differences in habitat. In the vertical direction, the structures are analogous in function due to similar lifestyles of organisms but anatomically different since they are part of different groups.
The prementum bears a structure called the ligula; this consists of an inner pair of lobes called glossae and a lateral pair called paraglossae. These structures are homologous to the lacinia and galea of maxillae. The labial palps borne on the sides of labium are the counterparts of maxillary palps.
The two pathways for homologous recombination in eukaryotes, showing the formation and resolution of Holliday junctions. The Holliday junction is a key intermediate in homologous recombination, a biological process that increases genetic diversity by shifting genes between two chromosomes, as well as site-specific recombination events involving integrases.