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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. 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 directionality is because RNA polymerase can only add nucleotides to the 3' end of the growing mRNA chain. This use of only the 3' → 5' DNA strand eliminates the need for the Okazaki fragments that are seen in DNA replication. [2] This also removes the need for an RNA primer to initiate RNA synthesis, as is the case in DNA replication.
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.
A distinct group of DNA-binding proteins is the DNA-binding proteins that specifically bind single-stranded DNA. In humans, replication protein A is the best-understood member of this family and is used in processes where the double helix is separated, including DNA replication, recombination, and DNA repair. [123]
Reverse transcription is the transfer of information from RNA to DNA (the reverse of normal transcription). This is known to occur in the case of retroviruses, such as HIV, as well as in eukaryotes, in the case of retrotransposons and telomere synthesis. It is the process by which genetic information from RNA gets transcribed into new DNA.
Eukaryotic Transcription. Eukaryotic transcription is the elaborate process that eukaryotic cells use to copy genetic information stored in DNA into units of transportable complementary RNA replica. [1] Gene transcription occurs in both eukaryotic and prokaryotic cells. Unlike prokaryotic RNA polymerase that initiates the transcription of all ...
Exposed single-stranded DNA can come under attack by endogenous mutagens, including DNA-modifying enzymes such as activation-induced cytidine deaminase, and can block replication forks to induce fork collapse and subsequent double-strand breaks. [24] As well, R-loops may induce unscheduled replication by acting as a primer. [12] [22]
Control of the DNA replication system ensures that the genome is replicated only once per cycle; over-replication induces DNA damage. Deregulation of DNA replication is a key factor in genomic instability during cancer development. [3] This highlights the specificity of DNA synthesis machinery in vivo. Various means exist to artificially ...