1. Reproduction & Genetics

2. Asexual Reproduction
Reproduction requiring one parent & leading to genetically identical offspring
Bacteria reproduce ‘asexually’… dividing by mitosis doubles the population
If mitosis were only strategy for reproduction, we would produce exact clones
(What would be the risk of having exact genetic copies of ourselves running around?)

3. Asexual Reproduction cont’d…
Asexual reproduction also requires less energy, and allows organisms to be more flexible in adverse environmental conditions, which can perpetuate the species as a whole.

4. Sexual Reproduction Vocabulary
Match the following definitions to the terms…
Gamete
Zygote
Fertilization
A cell formed by fusion of two gametes
Joining of male and female gametes
A male or female reproductive cell

5. Sexual Reproduction Vocabulary…
Haploid
Diploid
Meiosis
Cell that contains pairs of homologous chromosomes
Process producing cells containing half the number of chromosomes as the parent cell
Cell that contains half the number of chromosomes as the parent cell

6. Sexual Reproduction Requires two parents
Produces genetically unique offspring
Male gamete fuses with female gamete
A zygote is formed
gamete = haploid (n)
zygote = diploid (2n)
What is the human
haploid number?
diploid number?

7. Human Life Cycle

8. Benefits of Sexual Reproduction
In groups of 2-4
Take 10 minutes to research the benefits of sexual reproduction (vs. asexual reproduction)
Write your findings on chart paper to share with the class
“Why is sexual better than asexual?”

9. Meiosis (MY-OH-SIS)
The process that produces gametes with a haploid number of chromosomes.
Two key outcomes of meiosis:
Genetic Reduction
Genetic Recombination

10. Why meiosis?
If we reproduced only via mitosis… all cells would have 2n chromosomes.
If we added a sperm cell (2n) with an egg cell (2n) we would end up with a 4n zygote!
Additional chromosomes result in cell death or severe abnormalities.
Other benefits of meiosis?

11. Interphase
Cells dividing by meiosis will proceed through the G1, S, and G2 phases before dividing. This includes replication of chromosomes, taking place during the ____ phase. At the start of meiosis, the cell contains duplicated chromosomes.

12. Phases of Meiosis
Like mitosis, the events in meiosis can be grouped into four distinct phases: ______, ________, __________, and _________. Meiosis however, involves two complete cycles of the four phases. These two cycles are known as Meiosis I and Meiosis II.

13. Meiosis I
Prophase I
Pairs of homologous chromosomes line up side by side
This is called ‘synapsis’: aligning of homologous chromosomes during Meiosis I & II
Segments of chromosomes may be exchanged
Centrosomes move to poles, spindle apparatus forms

14. Metaphase I

15. Anaphase I

16. Result is two haploid daughter cells.
Telophase
Result is two haploid daughter cells.

17. Meiosis II
Phases of meiosis II are very similar to the phases of mitosis
Key difference:
Cell undergoing meiosis II is haploid
Cell undergoing mitosis is diploid

18. Meiosis II cont’d…
During metaphase II, single chromosomes line up along the equator
II I

19. Meiosis II cont’d…
During anaphase II, sister chromatids are pulled apart at the centromere
II I