Mutations KEY CONCEPT Mutations are changes in DNA

Mutations Some mutations affect a single gene, while others affect an entire chromosome. •

Mutations Gene mutation: mutations that affect a single genes • Point mutation-substitutes one nucleotide

Mutations More about gene mutations… t nd 2 lle bu • Frameshift mutation- inserts

Mutations Chromosomal Mutations: mutations that affect an entire chromosomes • Chromosomal mutations may occur

Mutations • More about chromosomal mutations… nd 2 lle bu t • Translocation results

Mutations Potential impact: Chromosomal mutations typically have a large effect on an organism; may

Mutations Silent: some mutations have no apparent effect • A point mutation may not

Mutations Mutagens: agents in the environment that can change DNA • Replication errors can

Mutations Summary Stuff: • Mutations in body cells do not affect offspring. • Mutations

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

Mutations 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.

Mutations Gene mutation: mutations that affect a single genes • Point mutation-substitutes one nucleotide for t e ull st b another 1 mutated base

Mutations More about gene mutations… t nd 2 lle bu • Frameshift mutation- inserts or deletes a nucleotide in the DNA sequence.

Mutations Chromosomal Mutations: mutations that affect an entire chromosomes • Chromosomal mutations may occur during crossing over t st 1 lle bu – Chromosomal mutations affect many genes. – Gene duplication results from unequal crossing over.

Mutations • More about chromosomal mutations… nd 2 lle bu t • Translocation results from the exchange of DNA segments between nonhomologous chromosomes.

Mutations 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

Mutations 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

Mutations 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.

Mutations 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.