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Slipped strand mispairing (SSM, also known as replication slippage) is a mutation process which occurs during DNA replication. It involves denaturation and displacement of the DNA strands, resulting in mispairing of the complementary bases. Slipped strand mispairing is one explanation for the origin and evolution of repetitive DNA sequences. [1]
Eukaryotes initiate DNA replication at multiple points in the chromosome, so replication forks meet and terminate at many points in the chromosome. Because eukaryotes have linear chromosomes, DNA replication is unable to reach the very end of the chromosomes. Due to this problem, DNA is lost in each replication cycle from the end of the chromosome.
This type of DNA damage would not accumulate with age, since once a cell was lost through apoptosis, its double-strand damage would be lost with it. Thus, damaged DNA segments undermine the DNA replication machinery because these altered sequences of DNA cannot be utilized as true templates to produce copies of one's genetic material. [1]
During DNA replication, the replisome will unwind the parental duplex DNA into a two single-stranded DNA template replication fork in a 5' to 3' direction. The leading strand is the template strand that is being replicated in the same direction as the movement of the replication fork.
Following annealing when replication occurs, the DNA is extended by a new sequence that is complementary to the molecule it is to be joined to. Once both DNA molecules are extended in such a manner, they are mixed and a PCR is carried out with only the primers for the far ends. The overlapping complementary sequences introduced will serve as ...
The replication of DNA with a broken sugar-phosphate backbone is most likely facilitated by the homologous recombination proteins that confer resistance to ionizing radiation. The activity of PRR enzymes is regulated by the SOS response in bacteria and may be controlled by the postreplication checkpoint response in eukaryotes.
Triplet expansion is caused by slippage during DNA replication, also known as "copy choice" DNA replication. [2] Due to the repetitive nature of the DNA sequence in these regions, 'loop out' structures may form during DNA replication while maintaining complementary base pairing between the parent strand and daughter strand being synthesized.
Image showing the formation of a DNA stem-loop (hairpin loop) DNA replication slippage occurs when the replication machinery encounters a repetitive sequence, such as a trinucleotide repeat region. [9] The repetitive nature of these sequences can present challenges during replication, as the template and newly synthesized strands can misalign.