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Any change to the quantity or the base sequence of
the DNA of an organism is known as a mutation
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Any change to one or more nucleotide bases, or a change in the sequence of the bases,
in DNA is known as a gene mutation
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Substitution of bases:
This is where a nucleotide in DNA is replaced by another nucleotide that has a different base
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If the final
base (cytosine) is replaced by guanine, then code becomes GTG that codes for histidine and replaces the
original amino acid glutamine
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Replacement amino acid may not form the same bonds
that determine the tertiary structure of a protein/ may
be a different shape and therefore not function
properly (like an enzyme with an inaccurate active site
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Gene Mutation

Deletion of bases:

Chromosome mutations:
This is changes in the structure or number of whole chromosomes
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is lost from the normal DNA sequence
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This is because the sequence of bases in DNA is read in 2
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One deleted nucleotide

Changes in whole sets of chromosomes: occur
when organisms have three or more sets of chromosomes rather than the usual two
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Changes in the number of individual chromosomes: sometimes individual homologous pairs of
chromosomes fail to separate during meiosis
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On fertilisation with a gamete that
has the normal amount of chromosomes, the resultant offspring have more or fewer chromosomes
than normal in tall their body cells
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Hybridisation and polyploidy:
Hybridisation is combining the genes of different varieties or species of organisms to produce a hybrid
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This can come about in different ways
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Gametes
could then be produced that have both sets (diploid rather than
haploid)
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Alternatively, if a diploid
gamete fused with a haploid gamete, the offspring would have
three sets of chromosomes (triploid)
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Gene Mutation



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