Review Where and in what form in prokaryotic DNA found Review Where is eukaryotic DNA found Infer What could be the result of damaged DNA being replicated

Ch 12 DNA 12.3 DNA Replication

Copying the Code Base pairing in the double helix explained how DNA could be copied Each strand has all the information Complementary strands Each strand could be used to make the other.

The Replication Process Process of a cell duplicating it’s DNA Ensures that each resulting cell has the same complete set of DNA molecules.

DNA molecule separates into two strands Produces two new complementary strands following base pairing rules Each strand is a template.

Two strands of the double helix separate, or “unzip,” allowing two replication forks to form.

New bases are added following the rules of base pairing.

Produces two DNA molecules identical to each other and to the original molecule Each molecule had one original strand.

The Role of Enzymes DNA polymerase Joins individual nucleotides to produce a new strand of DNA Proofreads DNA molecule.

Telomeres Tips of chromosomes Particularly difficult to copy DNA is lost during each replication Telomerase Special enzyme that some cells have that can rebuild the telomeres.

Replication in Living Cells Prokaryotic cells starts from a single point and proceeds in two directions until the entire chromosome is copied Have a single, circular DNA molecule in the cytoplasm.

Prokaryotic DNA Replication Replication starts until regulatory proteins bind to a single starting point on the chromosome.

Eukaryotic DNA Replication Replication may begin at dozens or even hundreds of places on the DNA molecule, proceeding in both directions until each chromosome is completely copied.

Two copies of DNA remain closely associated until the cell enters prophase of mitosis Chromosomes condense, and the two chromatids in each chromosome become clearly visible.