10 Really Important Things in Replication

1)  DNA always grows from 5' to 3'. The leading strand is always going into the fork, from 5' to 3'.

2)  DNA does not only replicate at the ends of the DNA at the fork.  The fork actually is part of a bubble, where DNA replicates on both ends.  And there are multiple bubbles on the DNA as it replicates.

3)  Initiation is the first stage of replication.  Helicase starts the process of replication in the DNA.  It unwinds the DNA.  Gyrase releases the tension in the DNA.  Single strand binding proteins (or SS binding proteins) keeps the separated strands stable.  RNA Primase creates primers for Polymerase III to attach to.

4) Elongation is the second stage of replication.  Polymerase III attaches to the DNA via the RNA Primers and adds bases.

5)  Termination is the final stage of replication.  DNA Polymerase I replaces the RNA Primer with DNA nucleotides.  It proofreads everything done so far.  Ligase glue the gaps in DNA caused by Okazaki Fragments.

6) Okazaki fragments occur because there are two strands in DNA replication:  leading and lagging strand.

Summary of points 1-6

7) Three types of bonds:  glycosol, phosphodiester, and hydrogen bonds.  Phosphodiester bonds along with sugar make up backbone of DNA.  Hydrogen bonds connect complementary bases.  Glycosol bonds sugar to DNA nucleotide (double check on Tuesday).

8)  DNA nucleoside is only sugar and nitrogenous base.  DNA nucleotide is sugar, nitrogenous base, and phosphate group put together.

Left side of diagram outlines where nucleoside and nucleotide begins.

9)  Counting carbons on a ribose:  DNA strand can only grow at carbon 3, and phosphate groups always bind to carbon 5.

10)  Anything that ends in -ase is an enzyme.  Strands in double helix are antiparallel.  One strand runs from 5' to 3' and the other from 3' to 5'.

11)... one more.  Watson and Crick came up with various models as to how DNA replicated.  The one that made the most sense was called semiconservative replication.  Happens when double helix separates so that each daughter molecule will have one old strand and one new strand.