1. Section 13.3/4: “Mutations & Gene Expression” Text Pages 372-376

2. What Are Mutations? Change in the genetic material of a cell
May occur in somatic cells (aren’t passed to offspring)
May occur in gametes (eggs & sperm) and be passed to offspring

3. Gene Mutations=produce changes in a single gene
Types of Mutations
Gene Mutations=produce changes in a single gene
Chromosomal Mutations=produce changes in whole chromosomes

4. Gene Mutations
Point Mutations=involve changes in one or a few nucleotides
Substitutions
Insertions
Deletions
(Generally occur during replication)
Frameshift Mutations=shifts the “reading frame” of a genetic message by inserting/deleting nucleotides

5. Substitution One base is changed to a different base.
Usually affects no more than a single amino acid.
Example: one codon of mRNA changed from CCC (proline) changed to ACC (threonine)

6. Insertions/Deletions
One base is inserted or removed—shifts the “reading frame”
Affects every amino acid following the mutation, altering the protein

8. Example—Gene Mutations
Sickle Cell disease is the result of one nucleotide substitution
Occurs in the hemoglobin gene

9. Example--Frameshift Mutation
Original:
The fat cat ate the wee rat.
Frame Shift (“a” added):
The fat caa tat eth ewe era t.

10. Amino Acid Sequence Changed (Deletion)

11. Gene Mutation Animation

12. Chromosome Mutations May Involve:
Changing the structure of a chromosome
The loss or gain of part of a chromosome
Types: Deletion, Duplication, Inversion, Translocation

13. Deletion
Loss of part of a chromosome

14. Duplication
Produces extra copy of all or part of a chromosome

15. Inversion
Reverses the direction of part of a chromosome

16. Translocation
Part of one chromosome breaks off and attaches to another.

17. Chromosome Mutation Animation

18. Are Mutations Helpful or Harmful?
Mutations happen regularly
Effects vary widely
have little or no effect (neutral)
produce beneficial variations (evolution)
negatively disrupt gene function (alter protein structure)
Chemicals & UV radiation cause mutations (mutagens)
Many mutations are repaired by enzymes

19. 13.4: Gene Expression
Gene regulation helps cells undergo differentiation or specialized in structure and function.
Example—As an embryo develops, different sets of genes are regulated, allowing them to become specialized
“Homeotic Genes”=Master control genes
Regulates organs that develop in specific parts of the body.