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Slide 1

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Polypeptide synthesis
Olivia Tate…read more

Slide 2

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Free nucleotides are moving within
the nucleus of a cell, the enzyme
helicase splits the two strands of
The section of DNA which is split is
specific to code for a particular
protein which is required
The free nucleotide bases for mRNA
(A,U,C&G) pair up to the
complimentary bases exposed
The strand of mRNA undergoes
splicing (described in next slide)…read more

Slide 3

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The pre-mRNA
molecule contains
Splicing both introns and
exons. The introns
are non-coding
bases therefore
When the DNA molecule is transcribed it these must be
removed before
contains non-coding areas of DNA, these are translation
also copied to form part of the mRNA molecule
The technique of splicing is carried out to
remove all non-coding areas of the pre-mRNA,
these non coding areas are called introns.
These introns must be removed from the pre-
mRNA molecules because they must not be
translated to produce a protein.
The coding parts of the pre-mRNA molecule are
called exons, these remain in the sequence of
bases and therefore form the mRNA molecule
The mature mRNA (normal
The mRNA molecule can then translated to mRNA), only contains exons
because only coding bases
produce a polypeptide must be present to
synethise a polypeptide…read more

Slide 4

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The strand of mRNA leaves the nucleus
through nuclear pores, it then travels
towards ribosomes
The tRNA is free around the mRNA, each
tRNA has a three base sequence called a
The codons on the tRNA bind to the
complimentary anti-codons on the mRNA
The tRNA then leaves the codon attached to
the anti-codon, each codon codes for an
individual amino acid
These amino acids polymerise together
forming the primary structure of a protein
During this water is eliminated as the
reaction is condensation…read more

Slide 5

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Amino acids and nucleotide base sequences
As you can see there
are many different
codons that code for
the same amino
acid. The two
nucleotide base
sequences are
important though.…read more

Slide 6

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Gene Mutation
A mutation is a unpredictable change in the DNA of an
organism, this usually is the change in the sequence of
nucleotide bases
If a specific section of DNA has mutated if can affect protein
This is because if the section of DNA codes for a specialised
protein, then a mutation of the nucleotide base sequence can
lead to non-functional proteins being formed or no protein at all
The amino acid sequence is important because this forms the
primary structure of a protein, the rest of the structure depends
upon this sequence
The coding for amino-acids is degenerate which means that the
last nucleotide base is non-specific which allows a number of
codons to be able to code for an amino acid (the next slide shows
This prevents the chance of a single mutation causing non-
functional proteins…read more

Slide 7

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