Genetics Notes - test 3

Genetics Notes - test 3 - Genetics Notes DNA replication...

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Genetics Notes: DNA replication Always have a break in dna backbone Nicked dna has single stranded cut – if no dna ligase Dna polymerase I ? breaks down dna and rna, breaks phosphodiester backbone Rna primer added by primase Mismatch repair – nick made in dna, mismatch base is removed, dna polymerase puts the complementary base in – dna ligase comes and seals it -see fig. 12.14 Fig 12.20: role of polymerase--- 5’ and 3’ ends are subjected to dnases that cut at each end Each replication chromosome will get shorter – nucleases shorten them too Protein plug on end? Eukaryotic: telomerase is a dna polymerase -cell provides trinucleotides -protein itself carries its own template and one to extend its sequence -3’ end has all it needs for replication -moves along repeating the same sequence – hundreds of times -extension of 5’ end… but needs a 3’ end -or an RNA primer can lay down and you get an okazaki fragment -work extremely fast Figure 12.19: -bacterial chromosomes are usually circular and have only one chromosome, but some have linear chromosomes, and some with more than one chromosome -telomeres: repeated sequences – short, at ends -the centromere binds proteins that associate with one another -primer is degraded one base at a time 12.10: -e coli –double stranded circular dna… could also be a plasmid in e coli -e coli takes 40 minutes to replicate its entire chromosome – one origin of replication -5 million base pairs total: dna polymerase adds 1000 bases per second (underestimate b/c enzyme has to back up to proofread) -diffusion: process that occurs at a very high rate of speed -eukaryotes have multiple origins of replication b/c they have 1000 X more dna -have to provide substrate -expenditure of energy by cells when they start replicating dna -cells have mechanisms to tell them whether to start replication or not -viruses (alytic) have to work rapidly to make enough to ensure survival (100-200) … when a virus is released, there’s no more substrate -can detect metabolism of cell to know how fast to work
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Genetics Notes - test 3 - Genetics Notes DNA replication...

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