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Mutations and Genetic Change

Mutations and Genetic Change. Section 14.1 Page. 319-324. Don’t call your little brother or sister a mutagen – they really aren’t !. What are mutations ?. Mutations are changes in the structure or amount of genetic material of an organism.

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Mutations and Genetic Change

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  1. Mutations and Genetic Change Section 14.1 Page. 319-324 Don’t call your little brother or sister a mutagen – they really aren’t !

  2. 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

  3. What causes mutations? Mutations occur as a result of: • natural, spontaneous mistakes in the cell cycle or • Environmental mutagens(any agent that can cause a change in DNA) • high energy radiation • chemicals: dioxins, asbestos, benzene, cyanide, formaldehyde • high temperatures

  4. Where’s the Histone?

  5. Types of mutations: DNA and Chromosomal – today we will only look at DNA types 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) • THE DOG BIT THE CAT. • THE DOG BIT THE CAR. • With the changing of a letter, the entire meaning of the sentence is changed

  6. Types of DNA 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 • Still codes for the amino acid Glycine!

  7. Types of DNA 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)

  8. Types of DNA 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) • THE DOG BIT THE CAT • THE DOB ITT HEC AT. (This ending is off by a frame!) • THE DOG BIT TTH ECA T(This ending is off by a frame!)

  9. Types of mutations Insertion or Deletion is an insertion or deletion of one or more nucleotides in a sequence Example: THE DOG BIT THE CAT. THE DOG BIT ETH ECA T. (Insertion) or THE DOG BIT THC AT. (Deletion)

  10. Types of DNA 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

  11. Page 320

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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)

  17. 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

  18. 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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