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Your Bio Rep posts godly notes.
LOL.
Joking.
All my bio notes will come under the label: Bio Notes.

The Idiot's Guide to DNA & GENOMICS
The fundamental facts

Actually I wanted to just do DNA replication and not the fundamental facts (which will have to do if you're doing DNA replication).
From my senior's experience, the chunk before DNA replication on your DNA notes won't be tested, but I feel you've to know them or else you'll get lost.

Here we go.

FUNDAMENTAL FACTS
Get this memorised and done with. It works wonders.

1. Nucleic acids

• 4th type of biological molecule (carbohydrates, proteins, lipids, nucleic acid)
• 2 types: Deoxyribonucleic acid and ribonucleic acid
• Stores and transmits genetic information

2. Nucleotide

• A nucleotide is the basic unit of a DNA/RNA. Many many nucleotides joined together becomes a DNA/RNA strand.
• For DNA it is called deoxyribonucleotide. For RNA, it is called ribonucleotide.
• Consists of a pentose sugar, a phostate group and a nitrogenous base.

-Pentose sugar:

• Pentose meaning there are 5 carbon atoms. 4C and 1O are linked in pentose formation, while carbon atom 5 protrudes out by a bond to carbon atom 4.
• In deoxyribonucleotides, carbon atom 2 is bonded to 2 hydrogen atoms.
• In ribonucleotides, carbon atom 2 is bonded to 1 H atom, 1 hydroxyl group (-OH). Which makes sense since they named them DEOXYribonucleotide and ribonucleotide.

-Phosphate group:

• Gives the nucleic acid its acidic properties.
• Drawing a phosphate group: P atom having 3 single bonds to O atoms (which means the O atoms are charge -1), 1 double bond to O atom.
• Realise that it is actually phosphoric acid, but the phosphate group is what we want to lock into our minds.

-Nitrogenous bases (2 types)

• Purines: Adenine and guanine
• Pyrimidines: Thymine, uracil and cytosine
• In short: DNA - ATCG, RNA - AUCG (T in DNA always replaced by U in RNA)

3. Formation of nucleotides

• Pentose sugar, phosphate groups and nitrogenous bases go through condensation reactions.
• Nitrogenous base (A,T/U,C,G) attached to carbon atom 1 of pentose sugar (OH from carbon atom 1 and H from nitrogen atom of base is removed as 1 water molecule)
• Phosphate group is attached to carbon atom 5 (OH from carbon atom 5 and H from one of the single bonded O atom is removed as 1 water molecule) now you know why you drew it as O-.

4. Formation of polynucleotides

• Via condensation reactions, carbon atom 3 of each nucleotide is attached to an O- of the phosphate group of another nucleotide.
• Thus there will be a sugar-phosphate backbone on one side, and nitrogenous bases on the other side.
• 5' end of the polynucleotide ends with a phosphate group attached to carbon atom 5 while the 3' end of the polynucleotide ends with hydroxyl group of carbon atom 3 sticking out alone (because no phosphate group condensed with it).

AWESOME.

With awesomeness,

Bio Rep.