DNA replication in 7 easy steps - BIOLOGY FOR LIFE

[Pages:19]DNA replication in 7 easy steps

1. Helicase enzyme breaks

hydrogen bonds between bases,

A protein that catalyzes chemical reactions.

unzips and unwinds the

helix

?Helicase begins to unwind the DNA at the ORIGIN OF REPLICATION (a specific DNA nucleotide sequence)

It's common to only show one strands sequence of bases, since the other can be inferred.

Helicase enzymes move in both directions from the Point of Origin, forming a REPLICATION BUBBLE.

At either end of the replication bubble is a REPLICATION FORK, a Y-shaped region

where the new strands of DNA are elongating.

In prokaryotic cel there is one origin

In eukaryotic cells there are 100's to 1000's of origins

What does it really look like?

1 2

3 4

BILL: define terms related to step 1

? Origin of replication ? Helicase ? Single strand binding

proteins ? DNA polymerase III ? Enzyme ? 3' end ? Nucleotides ? Primase

? Primer ? Deoxyribonoucleotides ? Antiparallel ? Replication fork ? Leading strand ? Lagging strand ? Okazaki fragment ? DNA polymerase I ? DNA ligase

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