Section 14.4 Mutations

Standard

• LS3.2 Explain how protein formation results in phenotypic variation and discuss how changes in DNA can lead to somatic or germ line mutations.

I Can…

• LS 3.2 I can predict how changes in the DNA nucleotides can lead to somatic or germ line mutations.

Key Questions

1. In what ways do mutations change genetic information?

2. How do mutations affect genes?

Vocabulary

• Mutation

• Point mutation

• Frameshift mutation

• Mutagen

• Polyploidy

Types of Mutations

• Mutations are heritable changes to genetic information.

• Mutations can be…• Gene mutations (point mutations)

• changes in the sequence of nucleotides in DNA

• Chromosomal mutations • changes in the number of structure of chromosomes

Gene Mutations- Point Mutations

• Point mutations change a single base pair.

1. Substitutions – one base is changed to a different base

2. Insertions – one or many bases are inserted

3. Deletions – one or many bases are removed

Gene Mutations- Point Mutations

Types of Substitutions

1. Silent – do not affect the amino acid sequence

2. Missense – changes one amino acid

3. Nonsense – changes codon into stop codon (causes translation to stop before protein is finished… could cause protein to be defective)

Examples for your 3 types of substitutions

Gene Mutations- Frameshift Mutations

• Insertions and Deletions are also known as frameshift mutations.

• Frameshift mutations • shift the “reading frame” of the genetic message

• Can change every amino acid that follow the point of the mutation

• Can alter a protein so much that it is unable to function normally

Frameshift Mutations

Chromosomal Mutations

• Deletion

• Duplication

• Inversion

• Translocation

Deletion

• 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

• Part of one chromosome breaks off and attaches to another

Effects of Mutations

• Genetic material can be altered by natural events or artificial means.

• The resulting mutations may or may not affect the organism.

• Many mutations are produced by errors in genetic processes.• DNA replication errors can cause point mutations (roughly once every 10

millions bases).

• Small changes in genes can gradually accumulate over time.

Mutagens

• Mutagens are chemical or physical agents in the environment that can cause mutations.

• Chemical mutagens examples• Certain pesticides, tobacco smoke, environmental pollutants

• Physical mutagens examples • Some forms of electromagnetic radiation, such as UV light

Harmful and Helpful Mutations

• Mutations are often thought of as negative, since they can disrupt the normal functions of genes.

• However, without mutations, organisms could not evolve.

• Mutations are the source of genetic variability in a species.

• The effects of mutations on genes vary widely. Some have little or no effect, some produce beneficial variations, and some negatively disrupt gene function.

Harmful Effects

• Dramatically change protein structure or gene activity

• Can disrupt normal biological activities and result in genetic disorders

• Some cancers are the product of mutations that cause the uncontrolled growth of cells.

Helpful Effects

• Mutations often produce proteins with new or altered functions that can be useful to organisms in different or changing environments.

• Example:• Over the past 20 years, mutations in the mosquito genome have many

African mosquitos resistant to chemical pesticides

Helpful Effects

• Plant and animal breeders make use of “good” mutations.

• Nondisjunction during meiosis can result in organisms that are triploid (3N) or tetraploid (4N).

• Polyploidy – condition in which an organism has extra sets of chromosomes

• Makes plants larger and stronger • Bananas, limes, and strawberries have been produced this way • Occurs naturally in some citrus plants (through spontaneous mutations)

Section 14.4 Exit Ticket

1. Describe the ways mutations can affect DNA and chromosomes.

2. What are the possible ways that a mutation may affect an organism?

The End