1 / 15

Mutations and Genetic Disorders

Mutations and Genetic Disorders. Mutations. “Changes in the DNA sequence that are inherited” Can have a negative consequence , no consequence, or a positive consequence. Types of Mutation. POINT MUTATION Silent Mutations Base pair substitution Mutations Mis-sense Non-sense

denver
Download Presentation

Mutations and Genetic Disorders

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Mutations and Genetic Disorders

  2. Mutations • “Changes in the DNA sequence that are inherited” • Can have a • negative consequence, • no consequence, or • a positive consequence

  3. Types of Mutation POINT MUTATION • Silent Mutations • Base pair substitution Mutations • Mis-sense • Non-sense 3. Frame Shift Mutations • Deletion • Insertion CHROMOSOMAL MUTATION

  4. 1.Silent Mutations • Has no consequence (neither good nor bad) • Can happen in 2 ways: • A mutation occurs in an intron, which is spliced out during mRNA processing. • A mutation occurs in the DNA which does not change the amino acid

  5. Silent Mutations - Example Example (No change in aa) 5’ – AUG AAG UUU GGC UAA – 3’ Met Lys Phe Gly Stop 5’ – AUG AAG UUU GGU UAA – 3’ Met Lys Phe Gly Stop Original (normal) mRNA Mutated (Base C changed to U) mRNA But no change in amino acid

  6. 2. a Missense Mutations • A change in a nitrogenous base leads to a change in the amino acid produced. Ex. Sickle Cell Anemia 5’ – AUG AAG UUU GGC UAA – 3’ Met Lys Phe Gly Stop 5’ – AUG AAG UUU AGC UAA – 3’ Met Lys Phe Ser Stop Original (normal) mRNA Missense mutation (G base changed to A) = A different amino acid

  7. 2. B Nonsense Mutations • A change in a nitrogenous base leads to a premature stop codon 5’ – AUG AAG UUU GGC UAA – 3’ Met Lys Phe Gly Stop 5’ – AUG UAG UUU GGC UAA – 3’ Met Stop Original (normal) mRNA Nonsense mutation (A base changed to U) = Premature stop codon

  8. Classification • Missense and Nonsense mutations arise because of a base pair substitution • In other words, the nitrogenous base itself may change, but the number of nitrogenous bases don’t change

  9. 3. A Deletion Mutations • One or more bases are deleted 5’ – AUG AAG UUU GGC UAA – 3’ Met Lys PheGly Stop 5’ – AUG AAG UUG GCU AA – 3’ Met Lys LeuAla Original (normal) mRNA Deletion of the base “U” = The “reading frame” shifts, and new amino acids result

  10. 3. B Insertion Mutations • The addition of one or more bases 5’ – AUG AAG UUU GGC UAA – 3’ Met Lys Phe Gly Stop 5’ – AUG UAA GUU UGG CUA – 3’ Met Stop Original (normal) mRNA Insertion of the base “U” = The “reading frame” shifts, and a stop codon results. This frameshift insertion cause a nonsense mutation

  11. Classification • Frameshift mutations occur because of insertions or deletions • NOTE: All of these mutations (missense, nonsense, insertions, deletions) are called point mutations meaning that they occur only with one base pair

  12. Classification • Another category of mutations involves large segments of DNA • These are called chromosomal mutations TRANSLOCATIONS INVERSIONS

  13. How do mutations arise? • What causes mutations? • List examples • Spontaneously • Mutagenic agents (chemicals that cause mutations, e.g. X rays, UV radiation, cosmic rays, chemicals)

  14. Try It! The following strand of mRNA represents the “normal” (aka wild type) strand. 5’ – AUG GGG UUU AUC CUA UAG – 3’ This strand is hit by UV radiation and turns into: 5’ – AUG GGG UUG AUC CUA UAG – 3’ • Write the amino acid sequences for both strands • What kind of mutation occurred? Be very specific. • What would happen if the “UUG” changed into “UAG”?

  15. Home Work • Pg # 263 , Q # 1 to 7

More Related