Theta replication

As in many such problems, some form of pretreatment of the data is warranted. In all applications discussed here, the analytical data either have been untreated or have been normalized to relative concentration of each peak in the sample. Quality Assurance. Principal components analysis can be used to detect large sample differences that may be due to instrument error, noise, etc. This is illustrated by using samples 17-20 in Appendix I (Figure 6). These samples are replicate assays of a 1 1 1 1 mixture of the standard Aroclors. Fitting these data for the four samples to a 2-component model and plotting the two first principal components (Theta 1 and Theta 2 [scores] in... 

FIGURE 25-3 Visualization of bidirectional DNA replication. Replication of a circular chromosome produces a structure resembling the Greek letter theta (0). (a) Labeling with tritium (3H) shows that both strands are replicated at the same time (new strands shown in red). The electron micrographs illustrate the replication of a circular E. coli plasmid as visualized by autoradiography, (b) Addition of 3H for a... 

Initiation of a second round of replication leads to a replication eye at the initiation site of replication (fig. 26.3). As synthesis proceeds the size of the replication eye becomes larger at this stage the replicating chromosome is referred to as a theta structure because it has the appearance of the Greek letter d. Semiconservative replication is consistent with the density of the autoradiographic tracks made by different parts of the chromosome after one and two rounds of replication in [3H]thymidine (see fig. 26.3). 

In land plants and algae, the prokaryotic fis and min genes involved in plastid division and cpDNA replication have been discovered. The products of the min genes-MinD and MinE-interact with the tubulin-like FtsZ protein, which participates in plastid division. FtsZ is encoded by a nuclear gene family. The minD and minE genes in C. vulgaris and G. theta are located in cpDNA. 

Replication in E. coli is a bidirectional process and is described by the theta model of replication. In this model the new strands peel from the parent strand, appearing like a Greek letter theta (0). There is strong evidence to support a model with two replication forks that work in concert in opposite directions starting from a well-defined initiation site. By the time the forks meet up, a complete second copy of the genome has been made (Fig. 8-3). 

To address these limitations, Prinzel etal. (1997)conductedasecondstudy that essentially replicated the experimental condilioiis described by Pope etal. (1995) with a few differences. Fiisf they examined system operation with the indices 1/alpha, beta/alpha, and beta/(alpha + theta). Also, the system configurahon used by Prinzel et al. was similar to the one used by Pope et al. except that EEG was recorded fiom only four sites Cz, Pz, P3, and P4. In addition, they analyzed the root mean square error (RMSE) on the tracking task. 

The main replication mechanisms for bacterial circular plasmids are theta-type, strand displacement, and rolling circle. Different elements are involved in this replication process this includes the ori site and the Rep protein gene which participate in the initiation of replication (del Solar et al. 1998). 

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