Mutations: Their Types and Effects
Name Class Date
13.3 Mutations
Lesson Objectives
Define mutations and describe the different types of mutations.
Describe the effects mutations can have on genes.
Lesson Summary
Types of Mutations Mutations are heritable changes in genetic information. There are two categories of mutations: gene mutations and chromosomal mutations.
Gene mutations produce changes in a single gene. Point mutations involve only one or a few nucleotides. Substitutions, insertions, and deletions are all types of point mutations.
In a substitution, one base is changed to a different base, which may affect only a single amino acid and have no effect at all.
In insertions and deletions, one base is inserted or removed from the DNA sequence. Insertions and deletions are called frameshift mutations because they shift the “reading frame” of the genetic message. Frameshift mutations can change every amino acid that follows the point of mutation and can have dramatic effects on the organism.
Chromosomal mutations produce changes in the number or structure of chromosomes. They include deletions, duplications, inversions, and translocations.
Deletion involves the loss of all or part of a chromosome.
Duplication produces an extra copy of all or part of a chromosome.
Inversion reverses the direction of parts of a chromosome.
Translocation occurs when part of one chromosome breaks off and attaches to another.
Effects of Mutations Genetic material can be altered by natural events or by artificial means. Errors can be made during replication. Environmental conditions may increase the rate of mutation. Mutagens are chemical or physical agents in the environment that cause mutations.
The effects of mutations on genes vary widely:
Some mutations have little or no effect.
Some mutations produce beneficial variations. One example is polyploidy in plants, in which an organism has extra sets of chromosomes. Polyploid plants are often larger and stronger than diploid plants.
13.3 Mutations
Lesson Objectives
Define mutations and describe the different types of mutations.
Describe the effects mutations can have on genes.
Lesson Summary
Types of Mutations Mutations are heritable changes in genetic information. There are two categories of mutations: gene mutations and chromosomal mutations.
Gene mutations produce changes in a single gene. Point mutations involve only one or a few nucleotides. Substitutions, insertions, and deletions are all types of point mutations.
In a substitution, one base is changed to a different base, which may affect only a single amino acid and have no effect at all.
In insertions and deletions, one base is inserted or removed from the DNA sequence. Insertions and deletions are called frameshift mutations because they shift the “reading frame” of the genetic message. Frameshift mutations can change every amino acid that follows the point of mutation and can have dramatic effects on the organism.
Chromosomal mutations produce changes in the number or structure of chromosomes. They include deletions, duplications, inversions, and translocations.
Deletion involves the loss of all or part of a chromosome.
Duplication produces an extra copy of all or part of a chromosome.
Inversion reverses the direction of parts of a chromosome.
Translocation occurs when part of one chromosome breaks off and attaches to another.
Effects of Mutations Genetic material can be altered by natural events or by artificial means. Errors can be made during replication. Environmental conditions may increase the rate of mutation. Mutagens are chemical or physical agents in the environment that cause mutations.
The effects of mutations on genes vary widely:
Some mutations have little or no effect.
Some mutations produce beneficial variations. One example is polyploidy in plants, in which an organism has extra sets of chromosomes. Polyploid plants are often larger and stronger than diploid plants.