Point Mutations

Transition Mutant (Substitution)

This is the exchange of a purine for a purine or a pyrimidine for a pyrimidine (A or G) or (C to T).

Transversion Mutant (Substitution)

This is the exchange of nucleotides outside of the nucleotide family; purine for a pyrimidine.

Transitions; transversions

________________ occur more often than ____________________ at a 2:1 ratio.

Silent Mutation (Insertion/Deletion)

This is changing one codon to a synonymous codon causing no change in the amino acid sequence of the protein; essentially no change.

Missense Mutation (Insertion/Deletion)

This is changing one codon to a different codon resulting in a change in the amino sequence of the protein; meaning changes but still understandable.

Nonsense Mutation (Insertion/Deletion)

This is changing one codon to a “STOP” codon resulting in premature stoppage of translation.

Frameshift Mutation (Insertion/Deletion)

This is the gain/loss of a nucleotide that result in change in the reading frame of the codon; does not make sense.

In-frame Mutation

This is the gain or loss of a nucleotide/trinucleotide set that does not change the reading frame of the codon; cuts a piece out.

Loss-Of-Function Mutation (Functional Mutation)

This results in a gene product with little or no functionality; amorphic.

Amorphic

This is when there is a complete loss of gene function.

Gain-of-Function Mutation (Functional Mutation)

This results in a gene product that has gained a new & abnormal function; neomorphic.

Neomorphic

This is when there is a new or different function from normal.

Lethal Mutation (Functional Mutation)

This is a mutation that leads to the death of the organism carrying the mutation.

Somatic Cells

These are non-sex cells; range from mild to severe; not passed to next generation.

Germ Cells

These are sex cells/gametes; typically more severe manifestations passed along to offspring.

Spontaneous

This is a mechanism of mutation where no artificial factor/external regulator causes the mutation.

Free Radicals (Environmental Induced)

These are very unstable & quick-reacting molecules that “steal” electrons from nearby stable molecules; induced by the environment.

UV Light (Environmental Induced)

This causes pyrimidine dimers by the formation of covalent linkages localized on cysteine double bonds.

5-Bromouracil (Chemical Induced)

This is a base analog or antimetabolite of uracil that can replace thymine in a strand of DNA.