Transcript Cell Mutations

Mutations
What is a mutation?
 Changes in the DNA sequence that affect
genetic information
• Normal:
Thesunwashotbuttheoldmandidnotgethishat.
The sun was hot but the old man did not get his hat.
• Translation changed in ribosome:
t hes unw ash otb utt heo ldm and idn otg ish at.
• Missing letter or base:
the sun wsh otb utt heo ldm and idn otg ish at.
Genetic mutations
 Not all are harmful
 Most cause little/no change
 Have to be reproductive cell mutations to
repeat in future generations
 Somatic mutations not inheritable
How do mutations happen?

Environmental agents
• UV light, chemicals,
radiation

Meiosis
• more/less chromosomes

Mistakes in DNA
replication
What happens when there is a mutation?

The mistake can cause the cell to make an incorrect
protein
• see a different phenotype than normal ex. White Buffalo

If the mutation occurs in a single type of cell,
• it will affect only the cell that carries it ex. Skin cells

If the mutation occurs in a sex cell,
• it can be passed to the offspring and affect their phenotype

Mutations can introduce genetic variation
• the change can be helpful, harmful or neither
Where do they happen?
 Gene Mutations
• replication
• transcription
• translation
 Chromosome Structural Changes
• Mitosis
• Meiosis
Gene Mutations
 Point Mutations
• involve one nucleotide
• single point in a DNA sequence
 Substitute one base for another
Gene Mutations
 Frameshift
•
•
•
•
insertion or deletion of a base
shifts entire sequence for translation
different group of amino acids
changes the protein function
Chromosome Structural Changes
 Deletion
- loss of all or part of
chromosome
- missing genes
may prove fatal
 Duplication
- segment repeated
- usually harmless
Chromosome Structural Changes
 Inversion
- connection broken &
sequence reversed
- may be fatal
 Translocation
- non-homologous
chromosomes sharing or
exchanging information