DNA Replication

McGraw Hill DNA Replication Movies the two strands of DNA are separated and then used as templates from which new strands are constructed does this before the cell divides (mitosis) DNA is anti-parallel (the two strands run in opposite directions)

DNA is semi-conservative—each molecule formed by replication consists of one newly formed strand (daughter strand), and one old strand (parental)

the enzyme helicase uncoils the double helix within the DNA molecule at sites called origins of replication/replication fork and splits it into two template strands DNA can only be replicated in one direction therefore, assembly is continuous on one strand (called the leading daughter strand) and discontinuous on the other (called the lagging daughter strand)

an enzyme acts as a primer and attaches short segments of RNA to both strands of DNA another enzyme starts replication next to this new RNA primer in only one direction. –it therefore moves away from the replication fork in the lagging strand and towards it in the leading strand copied at about 50 base pairs per second in animals in multiple areas on the DNA strand

on the lagging strand… –short lengths of DNA (called Okazaki fragments) are formed between RNA primers. –an enzyme removes the RNA primer added earlier and replaces it with DNA –another enzyme bonds the ends of adjacent DNA fragments together

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