DNA is a Double Helix - like a twisted rubber ladder made from three main components: sugarphosphate  Sides of the ladder are composed of phosphodiester bonds--a strong bond of alternating sugar and phosphate pieces bases  Each “rung” of the ladder is made up of two complementary bases  A bound to T C bound to G DNA is put together in chunks called NUCLEOTIDES

Consists of three parts:  Phosphate group (PO 4 3- )  Deoxyribose (sugar)  a nitrogen-containing base 1’ 2’3’ 4’ 5’ (see, no oxygen at 2’…)

Two WEAK H-Bonds Three WEAK H-Bonds

Purine Bases Pyrimidine Bases

If the DNA of one cell is stretched out, it makes a 7 ft. long string There are about 5 trillion cells in the human body If you connected all the DNA together, it would be long enough that 10 hours it would take over 10 hours to travel its length at light speed It takes nucleotides per second to replicate DNA In mammalian cells, there is one mistake in one billion during replication There are 10.4 bases in one full turn

The process of pulling the strands apart from each other and replacing each single strand with its complement is called REPLICATION

A DNA Helicase, an enzyme, separates the H- bonds and unwinds a small portion of the double helix

DNA Polymerase attaches to separated parental strands and matches up free nucleotides New Daughter Strand

Finally you have two identical copies of the double stranded DNA proofread each daughterThe final job of the DNA Polymerase is to proofread each daughter strand during and after the its synthesis

Cuts out nucleotides attaching upstream on the 3’ end Proofreads back on the 5’ end and cuts out improperly paired bases Unwinds DNA at the replication fork Unzips DNA (breaks apart Hydrogen Bonds)