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In evolutionary developmental biology, the concept of deep homology is used to describe cases where Cell growth and differentiation processes are governed by genetic mechanisms that are homologous and deeply conserved across a wide range of species.
Geoffroy's homology theory was denounced by the leading French zoologist of his day, Georges Cuvier, but in 1994, Geoffroy was shown to be correct. In 1915, Santiago Ramon y Cajal mapped the neural connections of the optic lobes of a fly, finding that these resembled those of vertebrates. In 1978, Edward B. Lewis helped to found evolutionary developmental biology, discovering that homeosis regulated embryonic development in fruit flies.
In 1997, the term deep homology first appeared in a paper by Neil Shubin, Cliff Tabin, and Sean B. Carroll, describing the apparent relatedness in genetic regulatory apparatuses which indicated evolutionary similarities in disparate animal features.
Within the metazoa, control differentiation along major body axis, and pax genes (especially PAX6) help to control the development of the eye and other . The deep homology applies across widely separated groups, such as in the eyes of mammals and the structurally quite different of insects.
Similarly, help to form an animal's segmentation pattern. HoxA and HoxD, that regulate finger and toe formation in mice, control the development of Actinopterygii in zebrafish; these structures had until then been considered non-homologous.
There is a possible deep homology among animals that use acoustic communication, such as songbirds and humans, which may share functional versions of the FOXP2 gene.
MGRSs are also known in medical terms as “pre-existing Polypoid Giant Cancer Cells (PGCCs)” and are frequently observed in untreated cancers. In cancer, the reproductive Germline cycle starts with a precursor cell. This cell will then polyploidize within a cell envelope. This cancer germ-line undergoes a process of development that is similar to the Entamoeba germline. A significant trace of deep homology can be found in mammalian germ-line stem cells. Based on a previous hypothesis, the germ-line is the common ancestor in somatic stem cell lineages. Daughter GSCs are the only stem cells that have the capability of passing genetic information throughout generations.
Difference from ordinary homology
Whereas ordinary homology is seen in the pattern of structures such as limb bones of mammals that are evidently related, deep homology can apply to groups of animals that have quite dissimilar anatomy: vertebrates (with made of bone and cartilage) and arthropods (with made of chitin) nevertheless have limbs that are constructed using similar recipes or "algorithms". (2017). 9781316601211, Cambridge University Press. ISBN 9781316601211
In cancer stem cells
In modern day biology, the depth of understanding deep homology has evolved into focusing on the molecular and Genetics and functions rather than simple morphology. Cancer stem cells (CSCs) are a population of cells within a tumor that have the ability to self-renew and differentiate into different cell types, similar to normal . The stem cell theory of cancer suggests that there is a subpopulation of cells, referred to as cancer stem cells, that have certain characteristics that make them unique among other types of cells within a cancer. The traits that are included in CSCs are that they multiply indefinitely, are resistant to chemotherapy, and are proposed to be responsible for relapse after therapy.
Life cycle of cancer
The unicellular life cycle of cancer and Entamoeba is uniquely similar, and thus contradicts the molecular phylostratigraphic theory for the origin of cancer. This deep relationship between the two cell systems is supported by the "amoeba model", which provides a greater understanding of the biology of cancer from the evolutionary perspective. The G + S life cycle of Entamoeba is the closest common ancestor than compared to any other life cycle of unicellular organisms. Similarly, both cell systems, amoeba and cancer, use the deep homologous G + S gene module that was evolved by a common ancestor. Some parallels that they share are too close for coincidence including:
Algorithm
In 2010, a team led by Edward Marcotte developed an algorithm that identifies deeply homologous genetic modules in unicellular organisms, plants, and animals based on (such as traits and developmental defects). The technique aligns phenotypes across organisms based on orthology (a type of homology) of genes involved in the phenotypes.
See also
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