DNA Mutations. Victims of Chernobyl - Mutations What are mutations? Mutations are a change in the...

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