MUTATIONS

1. MUTATIONS SC STANDARD B-4.9: The student will exemplify ways in which new characteristics are introduced into an organism or a population

2. Cornell Notes • Page 100 • Topic: Mutations • Essential Question: What is a mutation, how do mutations allow a species to change over time?

3. Mutation: The Basis of Genetic Change • A mutation is a change in the structure or amount of genetic material of an organism • In general, genetic differences among organisms originated as some kind of genetic mutation.

4. Causes of Mutations • Occur naturally as accidental changes in DNA or chromosomes • repair enzymes “overlook” errors • Rate of mutation can be accelerated by some environmental factors called mutagens • forms of radiation • chemicals

5. Effects of Mutations • Depends on where and when mutations occur • Germ Cell mutations • passed on to offspring • Somatic Cell Mutations • not passed on to offspring • could result in • Normal tissue • Cancer

6. Kind of Mutations • Mutations as changes in DNA • Point Mutation • change of a single nucleotide from 1 base to another • Insertion or Deletion • single nucleotide in a sequence added or dropped • rare

7. Point Mutation

8. Insertion or Deletion

9. Mutations as Changes in Results of Genes • Silent Mutations • has no effect on gene’s function • frequently happens because genetic code is redundant

10. Mutations as Changes in Results of Genes 2. Missense or Replacement Mutations codon changed so results in a different amino acid

11. Mutations as Changes in Results of Genes 3. Frameshift Mutations “reading frame” of a codon depends on the starting point insertions or deletions may shift the reading frame which may cause the remaining sequence of nucleotides to be “read” as different codons

12. Frameshift Mutations

13. Mutations as Changes in Results of Genes 4. Nonsense Mutation results when a codon is changed from an amino acid to a “stop” signal - resulting protein will be cut short & may fail to function

14. Nonsense Mutation

15. Mutations 5. More or Fewer Amino Acids if an insertion or deletion is a multiple of 3 the resulting protein will have fewer or more amino acids the more codons that are inserted or deleted the more likely the resulting protein will be malfunctioning

16. Chromosomal Mutations • In eukaryotic cells, the process of meiosis creates the chance of mutations at the chromosomal level: • involve changing the location of genes on chromosomes, or the numbers of copies of some genes

17. 4 Types of Chromosomal Mutations • 1. Deletions • Involve loss of all or a part of a chromosome • 2. Duplications • Produce extra copies of parts of a chromosome

18. 3. Inversions • Reverse the direction of parts of chromosomes • 4. Translocations • Occur when a part of one chromosome breaks off & reattaches on the end of another chromosome

19. Trisomies • 3 copies of a chromosome, in whole or in part • seen in several different chromosomes • most commonly in chromosome 21

21. Significance of Mutations • Neutral • most mutations • Lethal or Harmful • resulting proteins defective, disrupt normal activity • Beneficial • new altered protein offers individual advantages • Somatic cell mutations: affect individual only • Germ Cell mutations passed on to offspring • Basis for new genetic variation in population

22. Polyploidy • condition in which organism has extra sets of chromosomes (due to failure in meiosis) • Polyploidy plants often hardier, larger than diploid plants