1.1 Nitrogen containing base - adenine, cytosine,
guanine and cytosine
1.2 Deoxyribose/Pentose Sugar
1.3 Phosphate group
2.1 Adenine and guanine -
2.2 Cytosine and thymine -
purine bases/single ring
2.3 Adenine is
thymine - 2 hydrogen bonds
2.4 Cytosine is
guanine - 3 hydrogen bonds
3.1 Uracil replaces thymine
3.2 There is a ribose sugar
instead of a
3.3 It is single stranded whilst
DNA is double stranded
4 Protein Synthesis
4.1 Process by which
proteins are made in
1. Hydrogen bonds break between base pairs - DNA strands unzip
2. Free RNA nucleotides form complementary base pairs using one DNA strand as a template (produces mRNA strand)3. Newly formed mRNA strand leaves nucleus through nuclear pores.
1. mRNA strand binds to a ribosome
2. Amino acids in cytoplasm become attached to tRNA molecules (they are specific)
3. Anticodon on the tRNA binds to codon on mRNA molecule according to complementary base pairing.
4. Next codon from mRNA allows tRNA anticodon to bind. A peptide bond joins the amino acids.
5. Ribosome moves along the mRNA molecule until all amino acids are linked.
6. Polypeptide chain then dissociates from the ribosome.
5 Triplet Code
5.1 Code is degenerate as most
amino acids have 1+ triplet code
5.2 Non - overlapping -
each base is only
5.3 Three triplet codes don't code for any
amino acid (stop codes). They mark
the end of a polypeptide chain