1. Mutations Chromosomal Mutations (errors of cell division)
Point Mutations (errors of DNA replication)

2. Part 1: Chromosomal Mutations
Errors of Cell Division

3. Karyotypes Photograph of chromosomes, arranged by homologous pairs
First 22 pairs (in humans) are “autosomes”.
Last pair are sex chromosomes
XX = female, XY = male

4. Down Syndrome Female 47 XX +21
Aneuoploidy
Cells that have an abnormal number of chromosomes are aneuploid.
Normal Female 46 XX
Down Syndrome Female 47 XX +21

5. Some Common Aneuoploidies
X X X
Turner’s Syndrome
45 X
Triple X Syndrome
47 XXX

6. More Common Aneuoploidies
X X Y
X Y Y
Klinefelter’s Syndrome
47 XXY
XYY Syndrome
47 XYY

7. Anuoploidy Results from Nondisjunction of Sister Chromatids, During Mitosis or Meiosis

8. Errors Occur in Mitosis and Meiosis
Errors of Mitosis
Errors of Meiosis
Errors of mitosis are confined to daughter cells (not hereditary)
Called “somatic mutations”
Errors of meiosis are passed to every cell of an offspring
Called “germ line mutations”

9. Nondisjunction
Nondisjunction is the failure of chromosomes to separate during cell division, leading to asymetrical distribution between daughter cells.

10. Nondisjunction (continued)
Most chromosomal mutations of mitosis or meiosis are due to nondisjunction of sister chromatids, during anaphase (anaphase II in meiosis)
Additionally, in meiosis I, nondisjunction may occur between homologous chromosomes

11. Somatic Mutation
Somatic mutations occur in body (somatic) cells and affect only the daughter cells of the affected cell.
Moles and some cancers are the results of somatic mutations.

12. Nondisjunction can occur when spindle fibers from one centriole attach to both sister chromatids (mitosis & meiosis II) or both homologous chromosomes (meiosis I)
Spindle fibers from one centriole attaching to both sister chromatids

13. Mitosis: Metaphase
Homologous chromosomes
Sister chromatids

14. Chromosomes align across the “equator” of the cell, one sister chromatid on each side.

15. Mitosis: Anaphase
Nondisjunction of sister chromatids

16. Mitosis: Telophase & Cytokinesis
Nuclei form

17. Interphase Daughter cells are aneuoploid Karyotype: 2n + 1 (trisomy)
(monosomy)

18. Germ Line Mutation
Errors that occur in gamete production affect offspring.

19. Meiosis I: Metaphase Homologous chromosomes line up across the middle
Sister chromatids

20. Meiosis I: Anaphase
Nondisjunction causes both homo chromo’s to be in one cell

21. Meiosis I: Telophase

22. End of Meiosis I
2 aneuoploid daughter cells formed

23. Meiosis II: Prophase

24. Meiosis II: Metaphase
Chromosomes line up at “equator” of cell.

25. Meiosis II: Anaphase
Sister chromatids separate to opposite sides of cell.

26. Meiosis II: Telophase
4 aneuoploid haploid cells form (sperm or eggs)

27. Meiosis II: Telophase
Karyotype
N - 1
Karyotype
N + 1

28. Errors of DNA Replication
Part 2: Point Mutations
Errors of DNA Replication

29. Single Nucleotide Substitution

30. Deletion

31. The fat cat ate the big rat.
The frt cat ate the big rat.
The ftc ata tet heb igr at…..