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12.3 DNA Replication Notes
Transcript of 12.3 DNA Replication Notes
Before a cell divides, its DNA must first be copied.
How might the double-helix structure of DNA make that possible? What role does DNA polymerase play in copying DNA? Copying the Code The Replication Process Before a cell divides the DNA must be replicated Replication of DNA ensures all cells have the complete set of DNA Step 1: 2 strands are separated Each strand is used as a template Where the strand is separated is called the replication fork Step 2: Bases are added based on the base pairing rule Step 3: 2 strands of DNA formed Each strand of DNA formed contain 1 original piece and 1 new piece This is called
replication The Role of Enzymes in DNA Replication Helicase Unzips the DNA strand Breaks Hydrogen Bonds between nitrogen bases Joins individual nucleotides to produce the new strand of DNA Proofreads the new DNA strand makes sure bases have been added correctly DNA Polymerase Telomeres Tips of chromosomes Difficult region to replicate Enzyme known as telomerase
adds short DNA repeated sequence Lengthens chromosome
Making it less likely to lose part of a gene Prokaryotes vs Eukaryotes Prokaryotes Replication at a Single Point Proceeds in both directions
until chromosome is copied Eukaryotes Replication at many points Proceeds in both direction until chromosome is copied Most have one large Circular DNA Many chromosomes that are helical shaped Let's Review True/False: DNA must be replicated before a cell divides. True/False: In DNA replication 2 complementary strands are duplicated True/False: The double strand unwinds during replication True/False: DNA replication is catalzyed by enzymes called mutagens What enzyme is responsible for breaking the hydrogen bonds between nitrogen bases? What enzyme is responsible for adding nucleotides to the growing DNA strand? What does semi-conservative replication mean?