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Mutations and Genetic Change. Section 14.1 Page. 319-324. What are mutations ?. Mutations are changes in the structure or amount of genetic material of an organism. Organisms whose DNA or chromosomes have mutations are called mutants. What causes mutations?.

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Mutations and Genetic Change

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Mutations and genetic change

Mutations and Genetic Change

Section 14.1

Page. 319-324

What are mutations

What are mutations?

Mutations are changes in the structure or amount of genetic material of an organism.

Organisms whose DNA or chromosomes have mutations are called mutants

What causes mutations

What causes mutations?

Mutations occur as a result of:

  • natural, spontaneous mistakes in the cell cycle

  • mutagens (any agent that can cause a change in DNA)

    • high energy radiation

    • chemicals: dioxins, asbestos, benzene, cyanide, formaldehyde

    • high temperatures

Types of mutations

Types of mutations

Mutations as changes in DNA—when the wrong nucleotide may be paired or placed in a sequence during DNA replication

Point mutation is a change in a single base pair in DNA

Example: (When a letter is changed)



    • With the changing of a letter, the entire meaning of the sentence is changed

Types of mutations1

Types of mutations

Insertion or Deletion is an insertion or deletion of one or more nucleotides in a sequence



THE DOG BIT ETH ECA T. (Insertion) or

THE DOG BIT THC AT. (Deletion)

Types of mutations2

Types of mutations

Mutations as changes in the results of gene

  • Silent mutation is a mutation that has no effect on a gene’s function

    • These are often point mutations because many similar codons code for the same amino acid

  • Example: GGU, GGC, GGA, and GGG all code for the amino acid Glycine

Types of mutations3

Types of mutations

Missense mutation results when a codon is changed, the codon codes for a different amino acid

Example: AGC (codes for Serine) AGA (codes for Arginine)

Types of mutations4

Types of mutations

  • Frameshift mutation is a mutation in which a single base is added or deleted from DNA causing all the codons to be shifted one base

    • All codons after the mutation are affected

      Example: (When a letter is deleted)



Types of mutations5

Types of mutations

  • Nonsense Mutation results when a codon is changed to a “stop” codon

    • As a result an amino acid chain can be prematurely shortened and not make a complete protein

Page 320

Page 320

Chromosomal mutations

Chromosomal mutations

Chromosomal Mutations—the process of meiosis creates the chance of mutations at the chromosomal level

Deletion occurs when a piece of chromosome is lost

Duplication occurs when a piece remains attached to its homologous chromosome after meiosis

Chromosomal mutations continued

Chromosomal mutations continued

Inversion occurs when a piece reattaches to its original chromosome in a different direction

Translocation occurs when a chromosome piece ends up in a completely different, nonhomologous chromosome

Gene Rearrangement occurs when an entire gene moves to a new location

Mutations in reproductive cells

Mutations in reproductive cells

  • Occur when nucleotides change within a gene in a sperm or an egg cell

    • When these defective reproductive cells are mutated, the zygote that results can have structural and functional problems in the cells

  • If the mutation is so severe, the zygote will fail to grow

    • *Not all mutations are negative

    • Some mutations can make an organism faster, stronger, or better adapted for an environment

Mutations in body cells

Mutations in body cells

  • Mutations in these areas have no affect in later generations; problems only arise for the individual

  • Mutations that can lead to a loss of function such as a muscle or skin cell

    • When these cells divide, the mutation is copied also

  • Mutations in the genes that control cell division may lead to excessive cell growth called cancer

Large scale genetic change

Large scale genetic change

  • All 46 chromosomes are needed for a body to develop and function normally.

    • Organisms with missing chromosomes rarely survive

    • Organisms with extra chromosomes may survive but do not develop normally (ex. Down ’s syndrome)

Large scale genetic change1

Large scale genetic change

  • Nondisjunctionis when chromosomes fail to separate properly during meiosis

    • A parent’s gametes will receive two copies of a chromosome instead of one so when that mutated gamete combines with the other parent’s gamete, the child receives three copies

Large scale genetic change2

Large scale genetic change

  • Polyploidy is when an entire genome is duplicated and a cell ends up with multiple sets of chromosomes

    • More than two set (diploid)

    • Mostly occurs in plants

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