1.1 there are 2 forms: DNA
(deoxyribonucleic acid) and
RNA (ribonucleic acid)
188.8.131.52 Found in the Nucleus in a
Eukaryotic cell where it acts as
an information store.
184.108.40.206 Found in 3 different forms that are used
to read and translate the information to
produce various proteins that are
required to function.
1.2 The monomer of all Nucleic
Acids is called a Nucleotide
1.2.1 The Nucleotide is made up of 3 sub units: A
phosphate group, a sugar molecule and a
220.127.116.11 Joined by Covalent Bonds
18.104.22.168 There are 4 different Nucleotides, that have
the same Phophate group, either deoxyribose
sugar or ribose sugar and one of four different
22.214.171.124.1 Adenine, Guanine, Cytosine, Thymine (Thymine isn't
present in RNA so is replaced with Uracil)
1.2.2 Joining Nucleotides together.
126.96.36.199 Condensation Reaction between the Phosphate group
of one Nucleotide and the sugar of another Nucleotide.
188.8.131.52.1 Repeating this reaction gives a long chain of Nucleotides.
184.108.40.206.1.1 Forms a Sugar-Phosphate backbone.
1.2.3 The Organic Nitrogenous Bases are
grouped into either Purines or Pyrimidines.
220.127.116.11 Adenine and Guanine are Purines.
18.104.22.168.1 2 Ring Structure
22.214.171.124 Thymine, Uracil and Cytosine are Pyrimidines.
126.96.36.199.1 1 Ring Structure
188.8.131.52.2 Pyrimidines are smaller than Purines.
1.3 Too much Nucleic Acid causes Gout
1.3.1 Uric acid is produced when excess Purines are
broken down in the liver. It is then excreted in the
184.108.40.206 Some people have too much Uric acid in their blood. Uric acid is insoluble at lower
temperatures and forms crystals that are deposited in the joints at the extremities such as the
toes. The toe joint becomes very painful and swollen- a condition called Gout.
2.1 DNA is a long-chain polymer of nucleotide monomers.
The polymer is called a polynucleotide. A DNA molecules
forms when 2 polynucleotide strands come together
forming what looks like a ladder.
2.1.1 Hydrogen bonds form between the bases to strengthen the rungs of the ladder.
This gives DNA a very stable structure which is vital as it carries the instructions to
make an organism. If it were unstable the instructions could go wrong to easily.
2.2 The 2 DNA strand run parallel to each other and the space between them is taken up by the
Nitrogenous bases projecting inwards. The term 'Antiparallel is used because the strands run
in opposite directions to each other - the sugars are pointing in opposite directions.
2.2.1 The bases pair up in a specific way which keeps the chains the same distance
220.127.116.11 When a pyrimidine appears on one side a purine will
appear on the other.
18.104.22.168.1 Adenine pairs with Thymine (or Uracil in RNA)
22.214.171.124.3 As the pairs come together, Hydrogen
bonds form between the bases.
126.96.36.199.4 Base Pairing is described as
2.3 Making Copies of DNA
2.3.1 When a cell divides each new cell much receive a full set of instructions. Each
cell must have a full copy of all the DNA for that organism.
2.3.2 DNA replication takes place during the Interphase of the Cell Cycle.
2.3.3 1) DNA helix is
188.8.131.52 2) Helix unzips by the use of
the enzyme HELECASE.
184.108.40.206.1 3) The original DNA strand acts a template for the new RNA strand.
220.127.116.11.1.1 4) Free floating DNA Nucleotides bond to the exposed
bases by complementary base pairing rules.
18.104.22.168.1.1.1 5) Semi-Conservative Replication
22.214.171.124.126.96.36.199 6) Protein synthesis. The Hydrogen bonds break and the RNA is now
called mRNA which goes into the Ribosomes.
188.8.131.52.184.108.40.206.1 7) Primer signals tRNA to collect the Amino Acids and transport them to the Ribosomes.
220.127.116.11.18.104.22.168.1.1 8) RNA Polymerase is the enzyme that allows the Amino Acids to
bond together by the RNA code.
2.4 Structure and function in DNA
2.4.1 The sequence of bases is an example of information storage
because the information is in the form of codes that are used
to build Proteins.
2.4.2 The molecules are long so a
large amount of information can
2.4.3 The base-pairing rules means that the
complementary strand of information can be
2.4.4 The Double Helix structure gives the molecule stability.
2.4.5 Hydrogen Bonds allow easy unzipping for
copying and reading information.
3.1 Important structural differances between
DNA and RNA.
3.1.1 The sugar molecule
3.1.2 Contains the Nitrogenous
Base Uracil instead of
3.1.3 The poly-nucleotide chain is
usually single stranded.
3.1.4 3 forms of RNA molecule exist.
3.2 3 forms of RNA.
3.2.1 mRNA ( messenger RNA)
22.214.171.124 A strand that is complementary to a strand
of DNA (the template strand) it is therefore a
copy of the other DNA strand (the coding
strand) of the double helix.
3.2.2 tRNA (transfer RNA)
126.96.36.199 Carries Amino Acids to the Ribosomes where they are bonded
together to form Polypeptides.
3.2.3 rRNA (ribosomal RNA)
188.8.131.52 Found in the Ribosomes.
4.1 In 1953 at Cambridge, James Watson and Francis Crick discovered the
structure of DNA and worked out how it might form the instructions for life.
4.1.1 Their work and the key moment of
discovery owed much work that was done
by at the same time by Rosalind Franklin,
Raymond Gosling and Maurice Wilkins at
Kings College London.
184.108.40.206 The x-ray patterns they produced using DNA crystals enabled Watson and Crick to finally
piece together a full model of the structure of SNA that also explained how copies might be
made from it.