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Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a speciation event (orthologs), or a duplication event (paralogs), or else a horizontal (or lateral) gene ...
Homology among proteins or DNA is typically inferred from their sequence similarity. Significant similarity is strong evidence that two sequences are related by divergent evolution of a common ancestor. Alignments of multiple sequences are used to indicate which regions of each sequence are homologous. [40]
Homologous recombination also produces new combinations of DNA sequences during meiosis, the process by which eukaryotes make gamete cells, like sperm and egg cells in animals. These new combinations of DNA represent genetic variation in offspring, which in turn enables populations to adapt during the course of evolution .
This DNA must contain all of the parts necessary to complete the gene targeting. At a minimum this is the homology repair template, containing the desired edit flanked by regions of DNA homologous (identical in sequence to) the targeted region (these homologous regions are called “homology arms” ).
In both meiotic and mitotic cells, recombination between homologous chromosomes is a common mechanism used in DNA repair. Gene conversion – the process during which homologous sequences are made identical also falls under genetic recombination.
Selected portions of the DNA nucleotide sequence are copied into a corresponding RNA nucleotide sequence, which either encodes a protein (if it is an mRNA) or forms a 'structural' RNA, such as a transfer RNA (tRNA) or ribosomal RNA (rRNA) molecule. Each region of the DNA helix that produces a functional RNA molecule constitutes a gene. [15]
Subsequently, this nucleoprotein filament conducts a homology search in a homologous DNA region. Single-strand invasion in a complementary region in the homologous chromosome by the 3'-ended DNA strand forms a heteroduplex in the form of a displacement loop (D-loop). This D-Loop is extended as DNA repair synthesis occurs, forming a Holliday ...
Recombination hotspots are regions in a genome that exhibit elevated rates of recombination relative to a neutral expectation. The recombination rate within hotspots can be hundreds of times that of the surrounding region. [1] Recombination hotspots result from higher DNA break formation in these regions, and apply to both mitotic and meiotic ...