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A theta structure is an intermediate structure formed during the replication of a circular DNA molecule. Two replication forks can proceed independently around the DNA ring and when viewed from above the structure resembles the Greek letter "theta" (θ). [1] [2] Originally discovered by John Cairns, it led to the understanding that (in this ...
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.
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. Some eukaryotic viruses also replicate their DNA or RNA via the rolling circle mechanism.
The DNA model shown (far right) is a space-filling, or CPK, model of the DNA double helix. Animated molecular models, such as the wire, or skeletal, type shown at the top of this article, allow one to visually explore the three-dimensional (3D) structure of DNA. Another type of DNA model is the space-filling, or CPK, model.
The crystal structure of the Ter DNA-Tus protein complex (A) showing the nonblocking and the fork-blocking faces of Tus. (B) A cross-sectional view of the helicase-arresting surface. Replication of the DNA separating the opposing replication forks leaves the completed chromosomes joined as ‘catenanes’ or topologically interlinked circles ...
We also know that the replication-timing program changes during development, along with changes in the expression of genes. For many decades now, it has been known that replication timing is correlated with the structure of chromosomes. For example, female mammals have two X chromosomes. One of these is genetically active, while the other is ...
The process of semiconservative replication for the site of DNA replication is a fork-like DNA structure, the replication fork, where the DNA helix is open, or unwound, exposing unpaired DNA nucleotides for recognition and base pairing for the incorporation of free nucleotides into double-stranded DNA. [3]
DNA replication. The two base-pair complementary chains of the DNA molecule allow replication of the genetic instructions. The "specific pairing" is a key feature of the Watson and Crick model of DNA, the pairing of nucleotide subunits. [5] In DNA, the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine. The A:T ...