Transcript mutations
MUTATIONS Are they good or bad? Vocab you should know… Mutation: change in the nucleotide-base sequence of a gene or DNA molecule Deletion: loss of a part of DNA from a chromosome Inversion: reversal in the order of genes, or of a chromosome segment, w/in a chromosome More vocab… Translocation: movement of a segment of DNA from one chromosome to another, which results in a change in the position of the segment Nondisjunction: failure of homologous chromosomes to separate during meiosis I or the failure of sister chromatids to separate during mitosis or meiosis II Mutation basics Mutations are any change/“error” in DNA replication DNA replication is very accurate The enzyme DNA polymerase “proofreads” the copied DNA & repairs most mutations Mutations can be harmful, beneficial or have no effect at all More basics… Some mutations are caused by carcinogens – i.e. uv light, radiation, toxins Mutations that affect genes that control cell division lead to cancer b/c cancer is a tumor in which the cells begin dividing at an uncontrolled rate & become invasive (they spread out) Germ-Cell Mutations Occur in the gametes Don’t affect the organism itself Can be passed on to offspring during reproduction Somatic-Cell Mutations Occur in the body cells Can affect the organism i.e. cancers Cannot be inherited b/c they are not found in the gametes Lethal Mutations Often cause death, often before the organism is born Some can be beneficial – these are how natural selection occur (the organisms w/ beneficial mutations reproduce more often & spread that trait to their offspring) Chromosome Mutations Deletion: loss of a piece of chromosome Deletion Mutation – Rieger Syndrome Chromosome Mutations Inversion: section of chromosome breaks off & reattaches backwards Inversion Mutation – Hunter Syndrome Chromosome Mutations Translocation: piece of chromosome breaks off & attaches to a nonhomologous chromosome Chromosome Mutations Nondisjunction: chromosome fails to separate from its homologue during meiosis; resulting in one gamete receiving an extra copy of the chromosome (3 total) & another receiving none Nondisjunction – Down Syndrome Trisomy 21 Down Syndrome cont’d Mutation Quiz 1. 2. 3. 4. 5. Any error in DNA replication is a/an _____. What enzyme proofreads DNA & fixes most errors? What type of mutation occurs in gametes? Why are somatic-cell mutations not inheritable? A _______ mutation is when a chromosome losses a piece of itself. Mutation Quiz Cont’d 6. 7. 8. When part of a chromosome breaks off & reattaches backwards it is a ____ mutation. When a part of a chromosome breaks off & attaches to another chromosome it is a ______ mutation. When a chromosome fails to separate from its homologue it is a _______ mutation. Mutation Quiz Cont’d During nondisjunction one cell receives ___ copies of the chromosome, while another cell receives __. 10. Draw one of the phases of mitosis & label it. 9.