BIMM100 Problem Set 1 answers_JL_TAs(1)

Ii centromere 2 needed for segregating the chromosome

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Unformatted text preview: er” lagging strand fragments. DNA polymerase, nuclease, DNA ligase 3a. Write out an example of a telomeric repeat in humans. Label the 5’ and 3’ end. Which nucleotides are used to produce it? 5’ TTAGGG 3’ dTTP, dATP, dGTP 3b. What is the purpose of telomerase? What are its components? What does it do? What is the importance of the telomere. - Telomerase extends the 3’end of the template strand by reverse transcribing the telomerase RNA template. - Telomerase consists of a Reverse Transcriptase and an RNA. - It’s main purpose is to compensate for the shortening of DNA that is the by- product of nuclease activity on the “final” primer of the lagging strand during replication. - Telomeres provide protection from nucleases that might otherwise attack the DNA 3’end and they prevent the DNA 3’end from being recognized as a double strand break by the DNA repair machineries. 4a. What enzymatic activity does replicating DNA Polymerase have to correct errors during DNA replication? 3’5’ exonucleolytic activity. 4b. What’s the difference between the DNA substrates repaired by mismatch excision repair, base excision repair, and nucleotide excision repair? In which ways are these pathways similar? Mismatch excision repair corrects replication errors, base excision repair corrects chemically changed bases, and nucleotide excision repair fixes distorted DNA (e.g. thymine dimers). The pathways use different specific en...
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