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DNA Mutations
Victims of Chernobyl - Mutations
What are mutations?Mutations are a change in the
genetic material of a cell (i.e. the genes).
Key TermsMutation (Germ cell and Somatic)
◦Gene mutation◦Chromosome mutation
Point Mutation◦Substitution
Frameshift mutation◦Insertion◦Deletion
What can cause mutations?
These mutations can come from the environment (such as radiation = cancer) or they can come from errors in transcription and translation
2 Types of mutations
Germ cell mutation: These are mutations that occur in the sperm cell or egg cell. ◦ These mutations will be passed down from
parent to child
Somatic mutations: Occur in all other cells in the body◦ E.g. cancer
Where can mutations occur?
Gene mutations involve large segments of DNA or a single nitrogenous base.
Chromosome mutations occurs when an entire chromosome is lost or the structure of it changes
◦We will look at chromosome mutations later
2 Types of Gene Mutations
Point mutation- Substitution
Frameshift mutation - Insertion- Deletions
Point Mutation - Substitution
Substitution occurs when a single nitrogenous base is replaced with a different nitrogenous base
E.g.
Frameshift Mutations – Insertion/ Deletion
Insertion occurs when one or more nitrogenous base is added
Deletion: Occurs when one or more nitrogenous base is deleted
5 Possible Results of a Mutation
1. Silent Mutation
2. Substitution
3. Premature Stop
4. Codon Deletion or Insertion
5. Frame Shift
1. Silent Mutation (Point Mutation)
Occurs when a nitrogenous base is substituted but the change still produces the same amino acid.
E.g. AGA and AGG both produce the amino acid Arginine
1. Silent Mutation
2. Substitution (Point Mutation)
When an amino acid is substituted and the new codon makes a different amino acid
E.g. AGA makes Arginine and GGA makes Glycine
2. Amino Acid Substitution
3. Premature Stop (Point Mutation)
When a substitution results in the formation of a STOP codon.
This causes the amino acids after the STOP codon from being produced.
E.g. Original RNA AUGAAACAAGUUGCU
Mutated RNA AUGAAAUAAGUUGCU
4. Codon Deletion or InsertionA whole new amino acid is
added, or one is missing from the mutant DNA
E.g. Original RNA AUGAAACAA
Mutated RNA AUGGUUAAACAA
5. Frame ShiftWhen a deletion or insertion results in a
the shifting of codons causing a large change in the amino acids being produced
E.g. Original RNA AUGAAACAAGUC
Mutated RNA AUGAUAACAAGUC
5. Frame Shift
The Impact of DNA mutations
Silent mutations will not effect us because these mutations still produce the same amino acid
A substituted mutation that makes a s single different amino acid will have a small effect◦This is because only one amino acid
is changed
The Impact of DNA mutations
A premature STOP mutation will have a large impact because it will stop making the protein
A deletion mutation that removes an amino acid will often lead to a small impact.◦This is because only one amino acid
is affected
The Impact of DNA mutations
A frameshift mutation can have a severe impact because it can produce an entirely different protein
Examples
Sickle Cell Anemia (Substitution)
Colour Blindness (Substitution)
Examples
Thalassemia (Premature STOP codon)
Williams Syndrome (Deletion)
Tay-Sachs Disease (Frameshift)
Symptoms in infants include:
Slowing down of development Weakening of muscles Loss of motor skills such as turning
over, sitting, and crawling.
As the disease progresses, other symptoms may also occur, including:
Seizures Increased startle reflex to noise Vision loss Hearing loss Inability to swallow Mental retardation Paralysis Dementia