presentation

1. Meiosis &
Sexual Reproduction

2. Terms:
• Sexual reproduction
• Asexual reproduction
• Meiosis
• Gamete
• Chromosome
• Homologous chromosomes
• Karyotype
• Haploid
• Diploid
• Crossing over
• Independent assortment

3. Why sex?

4. Mitosis Meiosis

5. Gametes

6. Homologous Chromosomes

7. Karyotype
Karyotype Procedure

8. Diploid (2n=46)
Haploid (n=23)

10. Meiosis
Is the image above from a Diploid
or Haploid cell? How can you tell?

11. Meiosis
• Occurs in two main
stages
• Meiosis I
• Meiosis II

12. Crossing Over increases genetic
diversity of gametes

13. Crossing Over (Meiosis I)

14. Chromosome Pairs Align Randomly
During Metaphase I (Independent Assortment)
Also increases genetic diversity of gametes!

15. Nuclear envelopes form
around chromosomes,
which may temporarily
decondense. Spindle
disappears. Cytokinesis
may divide cell into two.
Homologous
chromosomes
separate to opposite
poles of cell. Sister
chromatids remain
joined.
Paired homologous
chromosomes align
along equator of cell.
DNA replicates.
Cell produces
proteins needed
for cell division.
INTERPHASE
TELOPHASE I &
CYTOKINESIS
ANAPHASE IMETAPHASE IPROPHASE I (LATE)PROPHASE I (EARLY)
Chromosomes
condense and become
visible. (2n = 4)
Crossing over occurs.
Spindle forms.
Nuclear envelope
breaks up.
Nucleus Nuclear envelope
Homologous
chromosomes
Centrosomes Spindle fibers
MEIOSIS I
Haploid (n)
Diploid (2n)
LM 25 μm LM 25 μm LM 25 μm LM 25 μm
(all) ©Ed Reschke
Meiosis I – Homologous pairs separate

16. Meiosis II – Sister chromatids separate

17. Fertilization Multiplies the Diversity
Gametes from 2 parents combine to form a genetically
unique zygote.

18. Independent assortment

19. Compare and Contrast Mitosis and Meiosis

20. Errors During Meiosis

21. Trisomy 21 = Down Syndrome

22. What can be learned from an amniocentesis?

23. Production of Gametes

24. Spermatogenesis

25. Oogenesis

26. Male or female?