DNA is made of NUCLEOTIDES​

Nucleotides are the building blocks of DNA and RNA​

​There are 5 different Nucleotides:

• Adenosine, ​Thymine, Cytosine, Guanine,

  and Uracil

• These are the 5 Different Nitrogenous Bases

Erwin Chargaff and his Rules​

Erwin Chargaff discovered DNA Composition​

Pyrimidines​: Thymine (T) and Cytosine (C)

• have a ONE ring structure

Purines: Adenine (A) and Guanine (G)​

• ​have a TWO ring structure

​Chargaff discovered that there was always equal amounts Thymine and Adenine, and Cytosine and Guanine in DNA​

DNA has a what is called a DOUBLE HELIX shape

• a double helix looks like a twisted rope ladder​

In this model, the entire strand is duplicated, and the original stays together​

Conservative:​

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In this model, each strand of the DNA is separated as a whole piece, and duplicated ​

Semi-Conservative:​

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In this model, the original DNA is ​chopped up into pieces, and dispersed throughout the two copies

​​Dispersive:

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Remember the Base pairings? ​These allow each side of the DNA strand to serve as a template for the new strand

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The Semi-conservative model is the correct one.

But how is DNA copied?​

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Step 1: ​DNA strands "unzip" at the weak Hydrogen bonds between Nitrogenous Bases

• ​The enzyme helicase is what actually does the unzipping

DNA ​polymerase adds new bases to the "template" strand of the DNA

These bases are taken from the Nucleus​

Step 2: ​The Complimentary Strand is made

Result: Two identical strands of DNA to split between new cells​

In Organic Chemistry, we number the carbons in a ​molecule

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These numbers are important for the structure of DNA​

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The Directionality of DNA​

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DNA Molecules have a "direction" (5' --> 3') and complimentary strands run in opposite directions​

• anti-parallel ​

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Replication occurs from 5' --> 3' on each strand​

Putting the DNA Backbone together occurs at the 3' end ​

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Any Questions?​