1.1.1 DNA is used to store genetic
information, which is all the
instructions needed to grow
and develop from an egg to a
fully grown adult.
1.1.2 DNA is stored in the
nucleus of a cell because it
is coiled so very tightly.
1.1.3 They are able to self-replicate because of their
paired structure so the genetic information can be
passed from generation to generation.
1.1.4 Genes are sections of DNA that code for
a specific sequence of amino acids that
forms a particular protein.
1.1.5 DNA is very long so it can hold
a lot of information in a small
amount of space.
1.2 What makes DNA?
1.2.1 DNA is a polynucleotide - it's made up of
lots of nucleotides joined together.
1.2.2 A nucleotide consists of a deoxyribose
sugar, a phosphate group and a
22.214.171.124 The base on each nucleotide can vary.
126.96.36.199.1 There are 4 possible bases;
adenine (A), thymine (T),
cytosine (C) and guanine (G)
188.8.131.52.1.1 A and G are a type of
base called a purine.
184.108.40.206.1.2 C and T are a type of
base called pyramidines
1.2.3 Nucleotides join together to form
polynucleotide strands. Two polynucleotide
strands join together and form an
antiparallel double helix.
220.127.116.11 They join up between the phosphate
group of one nucleotide and the sugar of
another (sugar phosphate backbone).
18.104.22.168 Two polynucleotide strands join together by hydrogen
bonding between the bases. Each base can only pair
with one particular partner - complementary base
pairing. T-A C-G
22.214.171.124.1 Two hydrogen bonds form between A
and T, and three between C and G
2 DNA Replication
2.1 1. The hydrogen bonds
between the polynucleotide
DNA strands break and the
2.2 2. Each original single strand
acts as a template for a new
strand. Free floating
nucleotides join to the
exposed bases on the
original template strand by
complementary base pairing.
2.3 3. The nucleotides on the new strand
are joined together by the enzyme
DNA polymerase. New hydrogen
bonds are formed.
2.4 4. Each new DNA molecule
contains one strand from the
old DNA molecule.
3 Protein Synthesis
3.1 Different proteins have a different number and order of
amino acids. It's the order of nucleotide bases in genes that
determine the order of amino acids in a particular protein.
3.2 Each amino acid is coded for by a sequence
of 3 bases in a gene. Different sequences of
bases code for different amino acids.
3.3 Ribosomes are found in the cytoplasm and
are responsible for protein synthesis. The
DNA molecules are too large to get out of the
nucleus so instead, the RNA leaves the
nucleus and joins with a ribosome in the
cytoplasm where it can be used to synthesise
3.4 DNA is copied into RNA for protein synthesis.
4.1 RNA is very similar to DNA in
that they are both made from
nucleotides containing sugar,
nitrogen-containing bases and
4.2 The structure of
RNA only differs in 3
4.2.1 The sugar in RNA nucleotides is
a ribose sugar, not deoxyribose.
4.2.2 The nucleotides form a
strand, not a double one.
4.2.3 Uracil, a pyramidine, replaces
thymine as a base and always
pairs with adenine in RNA.