Mutation

1. Mutation A permanent change in a cell’s DNA.

2. Cells have checkpoints to repair damage missed earlier in DNA replication. • Sometimes the cell doesn’t repair the damage. • If the damage goes unrepaired it can result in mutation.

3. Causes of mutations • A mutagen is a substance, such as a chemical, that causes mutations • Radiation (X rays) • UV light • Mutagens

4. main categories of mutations • Substitution: Involves a chemical change in one base pair. • Missense • Nonsense • Frameshift: The addition or loss of a nucleotide that results in a change of the “frame” of the amino acid sequence • Insertion • Deletion • Duplication: The copying of a nucleotide or amino acid sequence

5. Missense Mutation DNA = TAC GAG AGC CCA ATT RNA = AUG CUC UCG GGU UAA A.A. = Start leucine serine glycine stop DNA = TAC GAG CGC CCA ATT RNA = AUG CUC GCG GGU UAA A.A. = Start leucinealanine glycine stop A single base is changed to cause substitution of an amino acid.

6. Achondroplasia • Characterized by the improper development of the cartilage in legs and bones resulting in dwarfism

7. Nonsense mutation DNA = TAC GAG AGC CCA ATT RNA = AUG CUC UCG GGU UAA A.A. = Start leucine serine glycine stop DNA = TAC GAG ATC CCA ATT RNA = AUG CUC UAG GGU UAA A.A. = Start leucinestop A point mutation that results in a premature stop codon.

8. Muscular Dystrophy Characterized by the progressive weakening of many muscles in the body

9. Insertion mutations DNA = TAC GAG AGC CCA ATT RNA = AUG CUC UCG GGU UAA A.A. = Start leucineserine glycine stop DNA = TAC TGA GAG CCC AAT RNA = AUG ACU CUC GGG UUA A.A. = Start threonine leucine glycine leucine A mutation in which bases are added to the DNA sequence

10. Crohns Disease Characterized by chronic inflammation of the intestinal tract causing diarrhea, abdominal pain, nausea, fever

11. Deletion mutations DNA = TAC GAG AGC CCA ATT RNA = AUG CUC UCG GGU UAA A.A. = Start leucine serine glycine stop DNA = TAC AGA GCC CAA TTT RNA = AUG UCU CGG GUU AAA A.A. = Start serine arginine valine lysine A mutation in which part of the DNA is missing.

12. Cri Du chat • Characterized by a high pitched cry, similar to a cat, during infancy • Symptoms are lowered intellectual disability, delayed development, small head and weak muscle tone

13. Duplication DNA = TAC GAG AGC ATT RNA = AUG CUC UCG UAA A.A. = Start leucineserine stop DNA = TAC GAG GAG AGC ATT RNA = AUG CUC CUC UCG UAA A.A. = Start leucineleucineserine stop A type of mutation in which a portion of a genetic material or a chromosome is duplicated or replicated, resulting in multiple copies of that region.

14. Charcot-Marie Tooth Disease Characterized by damage to nerves leading to atrophy of muscles in hands and lower legs

15. Gene Translocation • The movement of a gene fragment from one chromosomal location to another, which can alter or abolish expression

16. Somatic vs. Germ Cell Mutation Somatic Germ • Mutation is passed on to offspring and will be present in every cell of the offspring • Alters mutated cell and future daughter cells • May cause no result in a cell if the particular sequence is not needed. • Cell death may occur • May lead to cancer

17. It’s estimated that mutations occur at the rate of 1 in every 50 million nucleotides. • This means that each new cell contains some 120 new mutations. Should we be worried? • NO – As much as 97% of our DNA does not encode anything. “junk DNA”

18. Mutation…Good? • Can mutations be beneficial to us? • Evolution – The changes seen in the inherited traits of a population from one generation to the next.