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DNA
· A DNA molecule contains 2
strands coiled together in a
double helix. Each strand is
made up of lots of small
groups called nucleotides.
Each nucleotides contains a
small molecule known as a
base. There are 4 different
bases adenine, thymine,
cytosine and guanine. They
always pair up in the same
way: a-t and c-g.…read more

Slide 3

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A gene is a small section of DNA and contains the
instructions or codes for one particular protein.
· Cells make proteins by joining a chain of amino
acids together in a particular order.
· It's the order of bases within a gene that instructs
the cell to put the amino acids together in a
particular order.
· The bases are read in triplets. Each triplet codes
for one amino acid. DNA also determines which
genes are or aren't active and so decides which
proteins the cell produces.…read more

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Proteins are made in the cytoplasm by ribosomes.
· The DNA contains the instructions for making
proteins but it is too big to leave the nucleus so
messenger RNA is made which is like DNA but
much smaller and only a single strand. It is made
by the DNA unzipping and a molecule of RNA is
made using a strand as a template.
· It moves out into the cytoplasm and joins to the
ribosome.…read more

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The cells of your body divide to
produce more cells for growth and
replacement of damaged cells. To do
this there are 2 stages. The first stage
involves the number of organelles
increasing and then the chromosomes
are replicated so that the cell has 2
copies of DNA within it. This happens
by the molecule of DNA split or
unzipping in the middle. The bases on
free-floating nucleotides attach to both
of the strands by base-pairing and
cross-links form between the bases
and the old DNA strands so there are
now 2 molecules of DNA.…read more

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The 2nd stage is the division. The
chromosomes line up in the middle of the cell
and the copies and the original chromosome
are pulled apart to opposite ends of the cell by
cell fibres. They form the nucleus of the new
cell and the cytoplasm divides.…read more

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