This document provides an overview of the key concepts and learning objectives related to sexual reproduction and meiosis. It discusses how genetic information is passed from generation to generation through homologous chromosomes and meiosis, which generates genetic variation in offspring. Meiosis involves two cell divisions that reduce the chromosome number by half to produce haploid gametes from a diploid cell, while crossing over and independent assortment during meiosis increase genetic variability in offspring.

1. Ch. 9 Sexual Reproduction
and Meiosis

2. Learning objectives for sexual
reproduction and meiosis
• Explain how genetic information is passed from one generation to the next
• Describe the role of homologous chromosomes in sexual reproduction
• Explain the purpose of meiosis and gamete formation
• Differentiate between haploid and diploid cells
• Diagram and identify the steps in meiosis
• Diagram and explain how meiosis generates genetic variability in offspring
• Compare and contrast the impact of crossing over, independent assortment and
random pairing during fertilization on variability in offspring
• Compare and contrast mitosis and meiosis
• Compare and contrast stem cells and differentiated cells.
• Compare and contrast preimplantation genetic diagnosis, genetic testing, and
gene therapy.
• Identify ethical issues associated with the use of DNA technology in medicine.

3. Why sex?

4. Homologous Chromosomes

5. Karyotype

6. Mitosis Meiosis

7. Gametes

10. Meiosis

12. Figure 9.7
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

14. Crossing Over

15. Chromosome Pairs Align Randomly
During Metaphase I

17. Fertilization Multiplies the Diversity

18. Compare and Contrast Mitosis and Meiosis

19. Errors During Meiosis

23. Production of Gametes

24. Spermatogenesis

25. Oogenesis

26. Male or female?

28. Figure 9.23
Diploid (2n = 4)
MEIOSIS I
Haploid (n = 2)
MEIOSIS II MEIOSIS II
Four haploid cells (n = 2)
Diploid (2n)
Haploid (n)
Haploid (n = 2)