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As with anatomical structures, sequence homology between protein or DNA sequences is defined in terms of shared ancestry. Two segments of DNA can have shared ancestry because of either a speciation event or a duplication event . Homology among proteins or DNA is typically inferred from their sequence similarity.
Homology among DNA, RNA, or proteins is typically inferred from their nucleotide or amino acid sequence similarity. Significant similarity is strong evidence that two sequences are related by evolutionary changes from a common ancestral sequence. Alignments of multiple sequences are used to indicate which regions of each sequence are homologous.
Mutations in a homeobox may change large-scale anatomical features of the full-grown organism. Homeoboxes are found within genes that are involved in the regulation of patterns of anatomical development ( morphogenesis ) in animals , fungi , plants , and numerous single cell eukaryotes . [ 2 ]
The comparative study of the anatomy of groups of animals shows structural features that are fundamentally similar (homologous), demonstrating phylogenetic and ancestral relationships with other organisms, most especially when compared with fossils of ancient extinct organisms.
Homology model of the DHRS7B protein created with Swiss-model and rendered with PyMOL. Homology modeling, also known as comparative modeling of protein, refers to constructing an atomic-resolution model of the "target" protein from its amino acid sequence and an experimental three-dimensional structure of a related homologous protein (the "template").
Especially for Hox proteins, which produce such dramatic changes in morphology when misexpressed, this raises the question of how each transcription factor can produce such specific and different outcomes if they all bind the same sequence. One mechanism that introduces greater DNA sequence specificity to Hox proteins is to bind protein cofactors.
Homeotic genes are genes which regulate the development of anatomical structures in various organisms such as echinoderms, [1] insects, mammals, and plants. Homeotic genes often encode transcription factor proteins, and these proteins affect development by regulating downstream gene networks involved in body patterning.
A protein superfamily is the largest grouping of proteins for which common ancestry can be inferred (see homology).Usually this common ancestry is inferred from structural alignment [1] and mechanistic similarity, even if no sequence similarity is evident. [2]