1. MUTATIONS
Are they good or bad?

2. 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

3. 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

4. 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

5. 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)

6. Germ-Cell Mutations Occur in the gametes
Don’t affect the organism itself
Can be passed on to offspring during reproduction

7. 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

8. 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)

9. Chromosome Mutations
Deletion: loss of a piece of chromosome

10. Deletion Mutation – Rieger Syndrome

11. Chromosome Mutations Inversion: section of chromosome breaks off &
reattaches
backwards

12. Inversion Mutation – Hunter Syndrome

13. Chromosome Mutations Translocation: piece of chromosome breaks off &
attaches to a nonhomologous chromosome

14. 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

15. Nondisjunction – Down Syndrome Trisomy 21

16. Down Syndrome cont’d

17. Mutation Quiz 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.

18. Mutation Quiz Cont’d
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.

19. 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.