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In molecular biology, [1] [2] [3] DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. [4] DNA replication occurs in all living organisms acting as the most essential part of biological inheritance .
In nature complementarity is the base principle of DNA replication and transcription as it is a property shared between two DNA or RNA sequences, such that when they are aligned antiparallel to each other, the nucleotide bases at each position in the sequences will be complementary, much like looking in the mirror and seeing the reverse of things.
The replicator is the entire DNA sequence (including, but not limited to the origin of replication) required to direct the initiation of DNA replication. The initiator is the protein that recognizes the replicator and activates replication initiation.
This also removes the need for an RNA primer to initiate RNA synthesis, as is the case in DNA replication. The non -template (sense) strand of DNA is called the coding strand , because its sequence is the same as the newly created RNA transcript (except for the substitution of uracil for thymine).
This figure shows DNA synthesis, but RNA synthesis occurs through the same mechanism. The cellular processes of DNA replication and transcription involve DNA and RNA synthesis, respectively. DNA synthesis uses dNTPs as substrates, while RNA synthesis uses rNTPs as substrates. [2] NTPs cannot be converted directly to dNTPs.
Rolling circle replication produces multiple copies of a single circular template. Rolling circle replication (RCR) is a process of unidirectional nucleic acid replication that can rapidly synthesize multiple copies of circular molecules of DNA or RNA, such as plasmids, the genomes of bacteriophages, and the circular RNA genome of viroids.
Reverse transcribing viruses replicate their genomes by reverse transcribing DNA copies from their RNA; these DNA copies are then transcribed to new RNA. Retrotransposons also spread by copying DNA and RNA from one another, [66] and telomerase contains an RNA that is used as template for building the ends of eukaryotic chromosomes. [67]
RNA-dependent DNA polymerases are a specialized class of polymerases that copy the sequence of an RNA strand into DNA. They include reverse transcriptase, which is a viral enzyme involved in the infection of cells by retroviruses, and telomerase, which is required for the replication of telomeres.