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Within frogs and fish, however, there exist fundamental differences in how convergent extension is achieved. Frog embryogenesis utilizes cell rearrangement as the sole player of this process. Fish, on the other hand, utilize both cell rearrangement as well as directed migration [1] (Fig. 1) . Cellular rearrangement is the process by which ...
A similar mechanism is thought to occur in tobacco plants, which show a high rate of gene transfer and whose cells contain multiple chloroplasts. [33] In addition, the bulk flow hypothesis is also supported by the presence of non-random clusters of organelle genes, suggesting the simultaneous movement of multiple genes.
"Strategies include the rearrangement of pre-existing tissue, the use of adult somatic stem cells and the dedifferentiation and/or transdifferentiation of cells, and more than one mode can operate in different tissues of the same animal. [1] All these strategies result in the re-establishment of appropriate tissue polarity, structure and form."
A large body of molecular evidence supports a variety of mechanisms for large evolutionary changes, including: genome and gene duplication, which facilitates rapid evolution by providing substantial quantities of genetic material under weak or no selective constraints; horizontal gene transfer, the process of transferring genetic material to ...
The information transfer may occur without physical exchange (a section of genetic material is copied from one chromosome to another, without the donating chromosome being changed) (see SDSA – Synthesis Dependent Strand Annealing pathway in Figure); or by the breaking and rejoining of DNA strands, which forms new molecules of DNA (see DHJ ...
The cell is the fundamental unit of structure and function in all living organisms. [14] The activity of an organism depends on the total activity of independent cells. [15] Energy flow (metabolism and biochemistry) occurs within cells. Cells contain DNA which is found specifically in the chromosome and RNA found in the cell nucleus and ...
At least some - it is presumed land-evolved - multicellularity occurs by cells separating and then rejoining (e.g., cellular slime molds) whereas for the majority of multicellular types (those that evolved within aquatic environments), multicellularity occurs as a consequence of cells failing to separate following division. [36]
Left unrepaired, these double-strand breaks can cause large-scale rearrangement of chromosomes in somatic cells, [20] which can in turn lead to cancer. [ 21 ] In addition to repairing DNA, homologous recombination also helps produce genetic diversity when cells divide in meiosis to become specialized gamete cells— sperm or egg cells in ...