Autonomously replicating sequences ARSs

The size of the genomic DNA in eukaryotic cells (such as the cells of yeast, plants, or mammals) is much larger (up to 10+11 base pairs) than in E. coli (ca. 10+6 base pairs). The rate of the eukaryotic replication fork movement is about fifty nucleotides per second, which is about ten times slower than in E. coli. To complete replication in the relatively short time periods observed, multiple origins of replication are used. In yeast cells, these multiple origins of replication are called autonomous replication sequences (ARSs). As with prokaryotic cells, eukaryotic cells have multiple DNA polymerases. DNA polymerase S, complexed with a protein called proliferating... 

Most progress in understanding this has been made in the yeast Saccharomyces cerevisiae from the chromosomes of which sequences have been identified that allow initiation of replication when inserted into plasmids (see below). These sequences are called autonomously replicating sequences (ARSs). It is likely that some of them, at least, represent bona fide replication origins. Presumably the mechanism of initiation at these origins is similar to that which has been elucidated in bacteria. 

As discussed In Chapter 4, replication of DNA begins from sites that are scattered throughout eukaryotic chromosomes. The yeast genome contains many 100-bp sequences, called autonomously replicating sequences (ARSs), that act as replication origins. The observation that Insertion of an ARS into a circular plasmid allows the plasmid to replicate In yeast cells provided the first functional Identification of origin sequences in eukaryotic DNA (see Figure 10-32a). 

Autonomously replicating sequences (ARSs) Sequences in yeast chromosomes that, when incorporated into an artificial plasmid, enable the plasmid to replicate efficiently in yeast cells. 

The answer is c. (Murray, pp 412-434. Scriver, pp 3-45. Sack, pp 3—29. Wilson, pp 99-121.) Despite the great length of the chromosomes of eukaryotic DNA, the actual replication time is only minutes. This is because eukaryotic DNA is replicated bidirectionally from many points of origin. The hundreds of initiation sites for DNA replication on chromosomes share a consensus sequence called an autonomous replication sequence (ARS). Thus, while the process of DNA replication in mammals is similar to that in bacteria, with DNA polymerases of similar optimal temperatures and speed, the many replication forks allow for a rapid synthesis of chromosomal DNA. Proteins such as histones, which are bound to mammalian chromosomes, inhibit DNA replication or transcription. Dissociation of the protein-DNA complex (chromatin) and unwinding of DNA supercoils (followed by chromatin reassembly) is part of the replication process. 

Arahidopsis thaliana 86 arabinose 680 archaeal phospholipids 513 aroma compounds 414 artemisinin 67 5 Arxula adenivorans 678 astaxanthin 616 ATP-citrate lyase (ACL) 679 autonomously replicating sequences (ARS) 696... 

Autonomously replicating sequence, ARS a DNA sequence that eonfers the ability to undergo high frequency autonomous transformation. Such sequences were first identified in the yeast, Saccharo-myces cerevisiae, in which they represent chromosomal origins of replication, and they have since been derived from a variety of eukaryotes including humans. Two important sequences are important for ARS function domain A [5 (A/T)TTTAT(A/G) TTT(A/T) 3 ] and domain B [5 CmTAGC(An ) (A/T)(A/T) 3 ]. Domain B is located 50-100 bp 3 to domain A. See Yeast artificial chromosome. 

Other spedalized DNA sequences, the Telomeres (see), are found at the ends of linear C Insertion of telomere sequences into a drcular plasmid converts it to a linear structure. Another type of sequence (see Autonomously replicating sequence, ARS) confers on plasmids the ability to replicate independently of the C, and may well be the sites at which replica-... 

Large sequences can be cloned circularly in yeast as yeast centromeric plasmids (YCps) in the presence of a yeast centromere (CEN) and at least one sequence that functions as a yeast replication origin (autonomously replicating sequence (ARS)). A YCp is... 

ARS Autonomously replicating sequence the origin of replication in yeast. 

ARS Automatic replicating sequence or autonomously replicating sequence... 

YCp Vectors The YCp yeast centromere plasmid vectors are autonomously replicating vectors containing centromere sequences, CEN, and autonomously repheating sequences, ARS. 

FIGURE 3.4 Yeast artificial chromosome (YAC) (TRPl, URA3 marker genes, ARS Autonomously replicating sequence, CEN centromere). 

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