Lecture on DNA replication termination and DNA ligation.
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Eukaryotes initiate DNA replication at multiple points in the chromosome, so replication forks meet and terminate at many points in the chromosome; these are not known to be regulated in any particular way. Because eukaryotes have linear chromosomes, DNA replication is unable to reach the very end of the chromosomes, but ends at the telomere region of repetitive DNA close to the end. This shortens the telomere of the daughter DNA strand. This is a normal process in somatic cells. As a result, cells can only divide a certain number of times before the DNA loss prevents further division. (This is known as the Hayflick limit.) Within the germ cell line, which passes DNA to the next generation, telomerase extends the repetitive sequences of the telomere region to prevent degradation. Telomerase can become mistakenly active in somatic cells, sometimes leading to cancer formation.
Additionally, to aid termination, the progress of the DNA replication fork must stop or be blocked. Essentially, there are two methods that organisms do this, firstly, it is to have a termination site sequence in the DNA, and secondly, it is to have a protein which binds to this sequence to physically stop DNA replication proceeding. This is named the DNA replication terminus site-binding protein or in other words, Ter protein.
Because bacteria have circular chromosomes, termination of replication occurs when the two replication forks meet each other on the opposite end of the parental chromosome. E coli regulate this process through the use of termination sequences that, when bound by the Tus protein, enable only one direction of replication fork to pass through. As a result, the replication forks are constrained to always meet within the termination region of the chromosome.[25] Source of the article published in description is Wikipedia. I am sharing their material. © by original content developers of Wikipedia.
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