DNA Replication AP Biology Regents Biology DNA Replication
DNA Replication AP Biology
Regents Biology DNA Replication… l THE PROCESS IS _________ l Meaning… ____________
Origins of Replication l Definition: ____________
Where does the energy originate to fuel this reaction? l ANSWER: ____________
Antiparallel Arrangement of DNA l What is meant by antiparallel? ? _______________
DNA Replication
Steps to DNA Replication l l l DNA unwinds using _____ and opens at _________________ is added to a strand by ______ so DNA polymerase can attach. At the __________DNA polymerase attaches and adds ____________ The other strand called _______ grows also in ___________ but in ______________ A DNA molecule replaces the primer and ______ glues the segments together
The DNA can repair itself! l DNA Polymerase proofreads first. l Mismatch Repair: Sometimes nucleotides are missed and the cell uses special enzymes to fix incorrectly paired bases. l Nucleotide Excision Repair: A nuclease cuts out the damage DNA and the gap is filled with the right nucleotides. l How can DNA be damaged? l What is a “thymine dimer”?
What is the purpose of a telemere? l THE PROBLEM: DNA can only be added to 3’ end – how to finish at 5’? Gaps are left and ends become shorter each time l THE SOLUTION: Telemeres do not contain genes but repeated nucleotide sequences (TTAGGG). As a result, as the chromosomes shortens only the repeated units shorten (telemere) rather than the genes!!!
What happens if the chromosomes gets too short ? l Telomerase helps restore the ENDS!!
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