DNA Replication

What is it? Replica – a copy of another’s work. Replication – the process of copying DNA Replication – the copying of DNA.

Why Copy DNA? In order for cells to function they need a set of instructions (DNA).

Why Copy DNA? During mitosis, when new cells are made the cells need a set of DNA.

How does DNA get copied? Three Major Steps: 1) A DNA Helicase enzyme attaches to DNA and unzips the bases down the middle.

How does DNA get copied? (continued) 2) Two DNA Polymerases move along each of the open sides of the DNA. * They bring in new nucleotides, from the cell, that are paired with the open bases.

How does DNA get copied? (continued) 3) The DNA Polymerase continues to add nucleotides to form two complimentary strands of DNA that are identical to each other.

DNA Replication Animations http://www.ncc.gmu.edu/dna/repanim.htm Animation (from start of the cell): http://www.lewport.wnyric.org/jwanamaker/animations/DNA%20Replication%20-%20long%20.html

Copying Errors? Sometimes nucleotides are incorrectly paired together, to prevent this from becoming a problem, DNA polymerase has a built-in “proof-reading” feature. DNA Polymerase can only add a new nucleotide if the previous one is correct.

How Fast? A single DNA molecule can have many DNA Polymerases and DNA Helicases all working at the same time. This greatly reduces the time needed to copy DNA.

Any Questions? “Eighty percent of success is showing up.” --Woody Allen “Never miss a chance to keep your mouth shut.” --Robert Newton Peck