1. MUTATIONS Slide 2MutationsMutations Slide 3Examples of MutationsExamples of Mutations Slide 4How Mutations occurHow Mutations occur Slide 5The Benefit of MutationsThe Benefit of Mutations Slide 6Rate of IncidenceRate of Incidence Slide 7Gene MutationsGene Mutations Slide 8Frame ShiftFrame Shift Slide 9Deletion and InversionDeletion and Inversion Slide 10Translocation and DuplicationTranslocation and Duplication Slide 11Whole Chromosome MutationsWhole Chromosome Mutations Slides 12 & 13PolyploidyPolyploidy

2. MUTATIONS Mutations are caused by Mutagens. Pathogens (Microbes and viruses) Radiation (Nuclear and Solar) Chemicals (smoking, herbicides, pollutants, diet, etc.) A carcinogen is a cancer causing mutagen. Mutations change the genetic information in a cell. If the cell is somatic then part of the organism will be affected. If the cell is a gamete then the entire offspring will be affected.

3. Normal red blood cell “Sickle” cell SOME MUTATION EXAMPLES

4. HOW MUTATIONS OCCUR One example of the process by which genetic information is changed: UV Light Thymine dimer DNA of tumour suppressor gene Lab manual page 140-2

5. BENEFIT Most mutations are harmful. Beneficial ones tend to occur more often in organisms with short generation times. Many may be silent – not observed – and may only be selected for or against at a later date. Neutral mutations make no change at all. Example: mRNA Amino acids Mutant DNA mRNA DNA This is known as Degeneracy – where multiple triplets code for one Amino acid.

6. Genes mutate at known rates. This rate varies depending on the gene involved. Some genes have high spontaneous mutation rates. Mutation rates for genes within a species are probably similar, but the viability of mutations varies greatly. Mutant genes in the human population: With approximately 30,000 genes in the human genome and two copies of each gene, each cell has a total of 60,000 genes. In higher organisms, a mutation for a specific gene will occur in one gamete in 300,000. Then one in five of us on average carries about 1 new mutant gene! Rates of Mutation 60,000 ÷ 300,000 = 0.2 = 20% Lab manual page 143

7. GENE MUTATIONS Mutations that affect one gene arise from point mutations – a change in the nucleotides on a DNA strand. Base mismatching - Missense substitution – may change one Amino Acid - Nonsense substitution Mutated DNA creates a STOP codon which prematurely ends synthesis of the polypeptide chain Normal DNA Mutant DNA mRNA Normal polypeptide e.g. Sickle cell anaemia

8. Insertion Deletion Causes a frame shift – it stuffs up the whole rest of the sequence. Large scale frame shift results in a new amino acid sequence. The resulting protein is unlikely to have any biological activity. Mutation: Insertion of C Original DNA Mutant DNA mRNA Amino acids Normal polypeptide Lab manual page 145, 9

9. CHROMOSOME MUTATIONS These can only occur during meiosis. a.k.a. Block mutations. Deletion: Inversion: Examples: Cru-Du-Chat, Prader-Willi Examples: On chromosome 2 – unviable offspring

10. Translocation: A section of one chromosome is lost to another one Duplication: A section of one chromosome is lost to its Homologue Chromosomes 9 and 22 – chronic leukaemia Chromosomes 9 – resulted in evolution of haemoglobin Lab manual page 150-1

11. WHOLE CHROMOSOME MUTATIONS Normal (Euploid) humans have chromosomes (2 exact sets). Aneuploidy is the term for having 1 or more missing or extra (not 2 sets). Monosomy = only one of a pair Polysomy = more than 2 of a pair, e.g. Trisomy = 3 homologues. This normally results from non-disjunction during meiosis. 46 Somatic cell Gametes Some examples: Trisomy chromosome 21 (Down’s) Monosomy sex chromosome (XO = Turner’s) Trisomy sex chromosome (XXY = Klinefelters) Lab manual page 153-7

12. POLYPLOIDY n = haploid (gametes) Usually only in plants. Allopolyploidy – from mating between 2 species. Autopolyploidy – from the same species. Often the initial hybrid is sterile, but as it reproduces asexually non- disjunction (amphiploidy) causes a doubling of the chromosome number… resulting in a fertile species. 2n = diploid (normal individual) 3n or more = polyploidy

13. Autopolyploidy Allopolyploidy Lab manual page 158-9, (160-1)