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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 ...
Instead, the SSA pathway only requires a single DNA duplex, and uses the repeat sequences as the identical sequences that homologous recombination needs for repair. The pathway is relatively simple in concept: after two strands of the same DNA duplex are cut back around the site of the double-strand break, the two resulting 3' overhangs then ...
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.
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.
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.
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 ...
Crossovers typically occur between homologous regions of matching chromosomes, but similarities in sequence and other factors can result in mismatched alignments. Most DNA is composed of base pair sequences repeated very large numbers of times. [29] These repetitious segments, often referred to as satellites, are fairly homogeneous among a ...
Synteny (in the modern sense) between human and mouse chromosomes. Colors in the human chromosomes indicate regions homologous with parts of the mouse chromosome of the same color. For instance, sequences homologous to mouse chromosome 1 are primarily on human chromosomes 1 and 2, but also 6, 8, and 18.