1. KEY CONCEPT Mutations are changes in DNA that may or may not affect phenotype.

2. Some mutations affect a single gene, while others affect an entire chromosome.
Many kinds of mutations can occur, especially during replication.
A mutation is a change in an organism’s DNA.

3. Gene mutation: mutations that affect a single genes
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Point mutation-substitutes one nucleotide for another
mutated
base

4. More about gene mutations…
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Frameshift mutation- inserts or deletes a nucleotide in the DNA sequence.

5. Chromosomal Mutations: mutations that affect an entire chromosomes
Chromosomal mutations may occur during crossing over
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Chromosomal mutations affect many genes.
Gene duplication results from unequal crossing over.

6. More about chromosomal mutations…
Translocation results from the exchange of DNA segments between nonhomologous chromosomes.
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7. Mutations may or may not affect phenotype
Potential impact: Chromosomal mutations typically have a large effect on an organism; may result in a disrupted gene or abnormal regulation of genes
Mutations may or may not affect phenotype
Point mutations may result in premature stop codons or amino acids with very different properties from the correct amino acid…
May disrupt a splice site
May disrupt a regulatory DNA sequence
Frame mutations may result in a completely altered protein or a premature stop codon
blockage
no blockage

8. Silent: some mutations have no apparent effect
A point mutation may not change the amino acid that is coded for
Even if a change occurs, the change may be in an intron that is removed & this has no effect
A change may not significantly affect the function of a protein if the new amino acid is similar to the correct one or occurs away from the active site or does not influence protein structure

9. Mutagens: agents in the environment that can change DNA
Replication errors can cause mutations.
Mutagens, such as UV ray and chemicals, can cause mutations.
Some cancer drugs use mutagenic properties to kill cancer cells.

10. Summary Stuff:
Mutations in body cells do not affect offspring.
Mutations in sex cells can be harmful or beneficial to offspring.
Natural selection often removes mutant alleles from a population when they are less adaptive.