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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.
Alignments of multiple sequences are used to indicate which regions of each sequence are homologous. [40] Homologous sequences are orthologous if they are descended from the same ancestral sequence separated by a speciation event: when a species diverges into two separate species, the copies of a single gene in the two resulting species are ...
The two pathways for homologous recombination in eukaryotes, showing the formation and resolution of Holliday junctions. The Holliday junction is a key intermediate in homologous recombination, a biological process that increases genetic diversity by shifting genes between two chromosomes, as well as site-specific recombination events involving integrases.
The pseudoautosomal regions or PARs are homologous sequences of nucleotides found within the sex chromosomes of species with an XY [1] or ZW [2] mechanism of sex determination. The pseudoautosomal regions get their name because any genes within them (so far at least 29 have been found for humans) [3] are inherited just like any autosomal genes.
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 ...
When mismatches occur in heteroduplex DNA, the sequence of one strand can be repaired to bind the other strand with perfect complementarity. During mitosis, the major homologous recombination pathway for repairing DNA double-strand breaks appears to be the SDSA pathway (rather than the DSBR pathway). [1]
During this process, Rad51 and Dmc1 recombinases bind the 3' single-strand DNA (ssDNA) tails to form helical nucleoprotein filaments that perform a search for intact homologous double-stranded DNA (dsDNA). [16] Once the homologous sequence is found, the recombinases facilitate invasion of the ssDNA end into the homologous dsDNA to form a D-loop.
Homology-directed repair (HDR) is a mechanism in cells to repair double-strand DNA lesions. [1] The most common form of HDR is homologous recombination. The HDR mechanism can only be used by the cell when there is a homologous piece of DNA present in the nucleus, mostly in G2 and S phase of the cell cycle. Other examples of homology-directed ...