Biology AS - DNA

DNA Structure:

• DNA: Double polynucleotide chains
• Sugar–phosphate backbone
• Deoxyribose Sugar joined to a Phosphate by a Phosphodiester bond
• Bases ( Thymine, Adening, Guanine and Cytosine) bonded together with Hydrogen Bonds

RNA Structure:

• RNA: Single polynucleotide chain
• Phosphate
• Ribose Sugar
• Base: Uracil, Adenine, Guanine and Cytosine

- Purine (two carbon-nitrogen rings) – e.g. Adenine & Guanine

- Pyrimidines (one carbon-nitrogen ring) – e.g. Cytosine, Thymine & Uracil

Semi Conservative Replication:

• The enzyme Helicase splits the DNA, which allows free bases in the surrounding solution to bond and form two new strands of DNA – with one original chain and one new chain

• The enzyme, Polymerase, is then used to form Phosphodiester bonds – this forms sugar phosphate backbone

ADP has a 2 phosphates, Ribose Sugar and Adenine

• When energy is used, a new Phosphate bonds with a Phosphate bond and forms ATP 
• Energy is stored in Phosphate bond and can be released to provide energy

rRNA Molecule:

• Catalyses formation of peptide bonds
• Large subunit
• Small subunit

tRNA Molecule: 

• Anticodon (3 bases)
• Intramolecular base pairings with Hydrogen bonds between
• Bonded together with a Amino Acid using a Ester Bond

Genetic Code:

• Base triplets (codons) code specific amino acids – non-overlapping
• Degrading genetic information: coded for by more than one codon
• Universal: same codons in all living things

- Polymerase unravels the DNA – one stand will be used as a template for mRNA

- Free RNA Nucleotides line up and form a complementary strand of mRNA

- This continues along the length of the DNA – hydrogen bonds reform and the DNA is put back together

- mRNA strand moves into Cytoplasm and joins to the tRNA and form Peptide bonds between Amino Acids – forms a protein

- tRNA then moves away, leaving a chain of Amino Acids