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The Hox genes 7, 8, and 9 correspond in these groups but are shifted (by heterochrony) by up to three segments. Segments with maxillopeds have Hox gene 7. Fossil trilobites probably had three body regions, each with a unique combination of Hox genes. Homeobox genes, and thus the homeodomain protein motif, are found in most eukaryotes.
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.
Phylogenetic analysis of homeobox gene sequences and homeodomain protein structures suggests that the last common ancestor of plants, fungi, and animals had at least two homeobox genes. [21] Molecular evidence shows that some limited number of Hox genes have existed in the Cnidaria since before the earliest true Bilatera , making these genes ...
In plants, however, the developmental genes affected by homeosis may control anything from the development of a stamen or petals to the development of chlorophyll. [2] Homeosis may be caused by mutations in Hox genes , found in animals, or others such as the MADS-box family in plants.
The B and C genes establish the identity of the stamens and the carpels only require C genes to be active. Type A and C genes are reciprocally antagonistic. [10] The fact that these homeotic genes determine an organ's identity becomes evident when a gene that represents a particular function, for example the A gene, is not expressed.
In plants, MADS-box genes are involved in controlling all major aspects of development, including male and female gametophyte development, embryo and seed development, as well as root, flower and fruit development. [12] [13] Some MADS-box genes of flowering plants have homeotic functions like the HOX genes of animals. [1]
An image of multiple chromosomes, taken from many cells. Plant genetics is the study of genes, genetic variation, and heredity specifically in plants. [1] [2] It is generally considered a field of biology and botany, but intersects frequently with many other life sciences and is strongly linked with the study of information systems.
From the example above, if the descendant with genes A1 and B underwent another speciation event where gene A1 duplicated, the new species would have genes B, A1a, and A1b. In this example, genes A1a and A1b are symparalogs. [1] Vertebrate Hox genes are organized in sets of paralogs. Each Hox cluster (HoxA, HoxB, etc.) is on a different chromosome.