Understanding Mutations: Types, Causes, and Inheritance in Genetics

1. MUTATIONS

2. MUTATIONS • ANY change in the DNA sequence that affects genetic information • Changes may be good or bad • There may or may not be a visible effect in an organism or its offspring…

3. So...when are mutations inherited? • Mutations will only be passed on to offspring if they occur in the gamete (sex cells)

4. When are mutations inherited? • Mutations that occur in regular body cells (somaticcells) will be lost when the cell dies • Mutation in lung cell will lead to cancer, but cancer isn’t passed on to offspring

5. When are mutations inherited? • Lethalmutations result in the death of the organism • Often miscarriage

6. What causes mutations? • No real known cause— • occur spontaneously • occur randomly

7. Mutagens may cause changes • X-rays • Ultraviolet rays • Microwaves • Cosmic radiation • Chemicals: • Benzene • Asbestos • Formaldehyde • Toxic industrial chemicals

8. Two Types 1. GENE MUTATIONS— • changes in a single gene 2. CHROMOSOMAL MUTATIONS— • changes in whole chromosomes (chromosome number or chromosome itself)

9. 1. GENE MUTATIONS a. POINT MUTATION (Substitution) • Single nucleotide is substituted for the wrong one • Ex: A-G instead of A-T • This can lead to…

10. 1. GENE MUTATIONS 1) Silent mutation: has NO effect since some amino acids have multiple sequences Ex: CUC codes for leucine CUA also codes for leucine

11. 1. GENE MUTATIONS 2) Missense mutation: causes the wrong amino acid to be in sequence Ex: CUU codes for leucine CCU codes for proline

12. 1. GENE MUTATIONS 3) Nonsense mutation: causes an early STOP codon Ex: UCA codes for serine UGA codes for STOP

13. THE FAT CAT ATE THE RAT THE FAT CAT ATE THE HAT POINT MUTATION—SUBSTITUTION

14. 1. GENE MUTATIONS b. FRAMESHIFT MUTATION • insertion or deletion of one or more nucleotides • All codons are shifted • May cause serious effects • Such mutations can alter a protein so that it is unable to perform its normal functions.

15. THE FAT CAT ATE THE RAT THE FAT CAT ATE THE RAT X TEF ATC ATA TET HER AT FRAMESHIFT MUTATION— DELETION

16. THE FAT CAT ATE THE RAT THE FAT CAT ATE THE RAT THE FLA TCA TAT ETH ERA T FRAMESHIFT MUTATION— INSERTION

17. 2. CHROMOSOMAL MUTATIONS a. DELETION • Involves loss of a part or whole chromosome

18. A A B C D D E E F F C DELETION

19. 2. CHROMOSOMAL MUTATIONS b. DUPLICATION • Opposite of deletion • A segment of the chromosome is repeated

20. A A B B C C D D E E F F B DUPLICATION

21. 2. CHROMOSOMAL MUTATIONS c. INVERSION • Direction of genes is reversed within chromosome (part is upside-down)

22. A B C D E F A E D INVERSION C B F

23. 2. CHROMOSOMAL MUTATIONS d. TRANSLOCATION • When part of a chromosome breaks off and relocates to another part

24. G A A G B H B H C C I I TRANSLOCATION D J J D K E K E F L L F

25. 2. CHROMOSOMAL MUTATIONS e. NONDISJUNCTION • Results in too few or too many chromosomes in a cell…

26. NONDISJUNCTION • MONOSOMY • Having only ONE copy of a chromosome instead of TWO • EX: Turner’s syndrome (has only one X chromosome)

27. NONDISJUNCTION • TRISOMY • Having THREE copies of a chromosome instead of TWO • EX: Down Syndrome (3 copies of chromosome #21, trisomy 21)

28. NONDISJUNCTION

29. Where can mutations occur? Somatic Cells (Body Cells) Germ Cells (Sex Cells)

30. Somatic Cells (Body Cells) • During or before mitosis • All new cells will also be altered • The change is permanent • Only effects organism, not offspring

31. Germ Cells (Sex Cells) • Changes can occur in egg/sperm before, during or after meiosis • Altered egg/sperm may be fertilized—passing change to offspring • Changes may or may not be harmful • Harmful changes cause birth defects