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Mutations

Mutations. Genetic Changes. What is a mutation ?. A change in the base sequence of DNA. What causes mutations?. Mistakes in replication (spontaneous) Mistakes in base pairs Environmental factors (mutagens) High energy radiation (X rays, UV rays)

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Mutations

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  1. Mutations Genetic Changes

  2. What is a mutation? • A change in the base sequence of DNA

  3. What causes mutations? • Mistakes in replication (spontaneous) • Mistakes in base pairs • Environmental factors (mutagens) • High energy radiation (X rays, UV rays) • Chemicals (asbestos, cyanide, formaldehyde) • High temperature

  4. A mutagen • Any agent that causes a change to the DNA sequence • High energy mutagens (radiation) break the DNA strands apart causing deletions or substitutions • Highly reactive mutagens (chemical) interact with the DNA usually causing substitutions

  5. Mutations in reproductive cells • Changes a sequence of nucleotides in a gene • May produce a new trait for the offspring

  6. Mutations in body cells • Change in the nucleotide sequence only effects the individual and will not be passed down to the offspring • i.e. Cancer, which effects genes that control cell division in mitosis

  7. Types of Mutations • Point mutations • Frameshift mutations • Chromosomal mutations • Deletion • Insertion • Inversion • Translocation

  8. Point mutations • A simple change in a single nucleotide base or “letter” of the gene sequence

  9. Point mutations • Original:   The fat cat ate the wee rat. • Point Mutation: The fat hat ate the wee rat (changing the r in cat to the h in hat). • This change alters the meaning of the instructions significantly. In DNA, switching one base in the DNA sequence to a different base canchange the protein that the gene makes.

  10. Frame-shift mutations • When one or more bases are added or deleted to the DNA strand. • It shifts the reading of mRNA codons by one base

  11. Frame-shift mutations • Original:   The fat cat ate the wee rat. • Frame Shift: The fat caa tet hew eer at. (the “t” from cat is removed) • This type of mutation can make the DNA code meaningless and often results in a shortened protein. 

  12. Frame-shift mutations

  13. Deletions • Occur when a part of the chromosome is left out.  • These can be small, such as the removal of just one "letter" or long enough to affect a large number of genes next to one another on the chromosome. • Deletions can also cause frame-shift mutations.

  14. Deletions • Original:  The fat cat ate the wee rat. • Deletion: The fat ate the wee rat. (deletion eliminated the word “cat.”)

  15. Deletions

  16. Insertions • Result in the addition of extra DNA. • Results is duplication of genes on the same chromosome. • May also cause frame-shift mutations, and they generally result in a nonfunctional protein. 

  17. Insertions • Original:  The fat cat ate the wee rat. • Insertion: The fat cat xlw ate the wee rat.

  18. Inversions • An entire section of DNA is reversed. • These can be small inversions within genes or large inversions that involve large regions of a chromosome and contain several genes.

  19. Inversions • Original:   The fat cat ate the wee rat. • Inversion: The fat eew eht eta tac rat.

  20. Translocations • Occur when a part of one chromosome breaks off and is added to a different chromosome

  21. Translocations

  22. Mutation Examples

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