genetic mutations. mutation: an unpredictable change in the genetic material of an organism gene...
TRANSCRIPT
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Genetic Mutations
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Mutation:An unpredictable change in the genetic
material of an organism
Gene Mutation:A change in the structure of a DNA molecule,
producing a different allele of a gene (allele = version of a gene; ex: brown hair,
black hair)
Chromosome Mutation: A change in the entire structure or number of
whole chromosomes
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Causes of Mutations
Mutations occur randomly with no obvious cause.
Mutagens: Substances that increase the chances
of mutation occurring
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Types of Mutations
• Base Substitution – One nucleotide base takes the place of another
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• One amino acid is changed in the sequence
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Base Substitutions
• Missense = if substitution changes amino acid
• Nonsence = if substitution changes amino acid into a “stop” codon
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Types of Mutations
• Base Addition – (aka Insertions) One or more extra nucleotide bases added to a sequence
• Base Deletion – One or more nucleotide bases are lost from the sequence
**Both additions and deletions cause
Frame Shift Mutations
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• Incorrect sequence of amino acids
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• Incorrect sequence of amino acids• Frame Shift Mutations
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Silent mutations – Mutation that has no apparent effect on an organism OR does not change the amino acid
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Which types of mutations have the greatest impacts?
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Sickle Cell Anemia
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Sickle Cell Anemia• Base substitution with a significant side effect on
phenotype
• The affected gene codes for the oxygen carrying pigment HAEMOGLOBIN.
Normal Amino Acid Sequence:Val-His-Leu-Thr-Pro-Glu-Glu-Lys-
Sickle Cell Anemia Sequence:Val-His-Leu-Thr-Pro-ValVal-Glu-Lys-
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• When haemoglobin is not combined with oxygen, the β chains are less soluble causing them to stick to each other.
• This pulls RBC’s out of shape into a sickle shape.
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Phenylketonuria (PKU)
• Base substitution
• The affected gene codes for an enzyme (phenylalanine hydroxylase), which is not present in people with the mutation
• This enzyme helps catalyse the conversion of phenylalanine to triosine, which is then converted to melanine
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Effects of PKU
• Lighter skin colour
• Accumulation of phenylalanine in blood and tissue fluid, causing severe brain damage
• Babies are tested for PKU at birth for prevention
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Environmental Impacts on Phenotype
• Some alleles code for traits that are highly impacted by environmental factors, such as height.
• Diet
• Temperatures