38_printout - Lecture 38: DNA replica2on in...

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Unformatted text preview: Lecture 38: DNA replica2on in eukaryotes Lecture 38 (4/7/11) DNA replica2on, con’t. Reading assignment: pp. 991 ­3, 1053 ­6. Eukaryote DNA Replica2on 1.  Eukaryote genomes are large; organized into mul2ple chromosomes. 2. DNA synthesis is ini2ated not from one but numerous replica2on origins on each chromosome. 3. Rate of replica2on is regulated by the number of replica2on origins used. 4. Replica2on ini2a2on is under both cell cycle and developmental regula2on 5. Eukaryote chromosomes are linear and have ends known as telomeres that are synthesized by a specialized DNA polymerase 1 Lecture 38: DNA replica2on in eukaryotes Eukaryote chromosomes are very long Mul4ple replica4on origins/chromosome Q: Are replica2on origins defined by specific sequences? •  Eukaryote chromosomes contain mul4ple replicons. •  Replica4on origins in the yeast Saccharomyces cerevisiae are well ­ defined AT ­rich DNA sequences of about 100 ­150 bp that contain the consensus sequence 5’ A/T TTT ATGTTT A/T 3’. •  Such sequences, when cloned into bacterial plasmids, allow the plasmids to replicate in yeast. •  In mammalian cells, replica4on ini4a4on appears to occur at discrete loca4ons but so far, specific DNA sequences that confer autonomous replica4on to plasmid DNA have not been iden4fied. 2 Lecture 38: DNA replica2on in eukaryotes DNA replica2on is under cell cycle regula2on Fig. 26 ­39 Nelson & Cox. Lehninger Principles of Biochemistry, 5th ed. Freeman Publishing Company. 3 Lecture 38: DNA replica2on in eukaryotes Greider Blackburn Szostak 4 ...
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