1. Chapter 7 Meiosis & Sexual Reproduction (Stem Cells)
Section 1 – Meiosis
Section 2 – Sexual Reproduction

2. Stem Cells Definition: Cells that have three specialties:
They have the capability to differentiate into a specialized cell or remain as a stem cell
Provide repair to tissues or organs after long periods of inactivation
Can continuous divide when needed

3. Stem Cell Research Embryonic Stem Cells
Rare cells found in adult organs or tissues that are undifferentiated
Usually limited capacity to original origin
Adult Stem Cells
Only derived from eggs fertilized In Vitro
Growth is performed in a laboratory for research purposes (not in a mother’s womb)
In vitro fertilization—A technique that unites the egg and sperm in a laboratory instead of inside the female body.

4. Ethical Question
Is it ethically right to possibly destroy a human embryo to remove stem cells for future medical treatment?

5. Stem Cells

6. Meiosis
A form of cell division that produces haploid cells – gametes or spores that contain half the amount of chromosomes
Before meiosis – DNA must be replicated
Homologous chromosomes are used for meiosis
End result: Four genetically different cells

7. Prophase i Chromosomes condense – nuclear envelope breaks down
Homologous chromosomes pair up lengthwise
Crossing-over: exchanging of parts of the chromatids

8. Metaphase i The pairs of chromosomes are moved by spindle fibers
They line-up on the “equator” or metaphase plate of the cell
No part of chromosome is separated

9. Anaphase i
Whole pairs are pulled to opposite poles of the cell by the fibers
Chromatids DO NOT separate
Half are pulled to the North
Half are pulled to the South

10. Telophase i Chromosomes gather at their respective poles
Nuclear envelope develops around each pole
Cytoplasm divides through cytokinesis

11. Prophase ii
New spindle fibers form
Nuclear envelope breaks down

12. Metaphase ii Same as Metaphase I
The pairs of chromosomes are moved by spindle fibers
They line-up on the “equator” or metaphase plate of the cell
No part of chromosome is separated

13. Anaphase ii NOT the same as Anaphase I
Centromeres are divided – separates the chromatids from their pair
Chromatids are pulled to separate poles and now named chromosomes
One half of pair moves East and other moves West

14. Telophase ii Same as Telophase I
Chromosomes gather at their respective poles
Nuclear envelope develops around each pole
Cytoplasm divides through cytokinesis
End Product: Unpaired chromosomes – genetically different from one another

15. Independent assortment
Random distribution of chromosomes during meiosis
Randomness is based on starting position, one switch can cause a whole different outcome

16. Crossing-over
The process that occurs before independent assortment that creates an unlimited number of possibilities
Randomness starts when the sperm fertilizes the egg

17. Importance of Genetic Variation
Genetic variation allows for faster evolution
As genes are used up – the process becomes more difficult
Natural selection however does not always favor genetic variation which can slow evolution down

18. Meiosis in Males
Spermatogenesis: sperm production in the testes in male organisms (occurs daily)
The sperm cell growths through meiosis I and produces four functional sperm through meiosis II
Sperm looks like a tadpole – small body with a long tail

19. Meiosis in females
Oogenesis: egg production in the ovaries in female organisms (happens once in the womb)
Only one functional egg is produced during one full cycle of meiosis
Cytoplasm is split unevenly during meiosis I

21. Sexual & asexual reproduction
a process of where a single parent passes on an exact copy of its genes to its offspring
Clone: offspring that is genetically identical to its parent
Sexual Reproduction:
a process where two parents participate to develop genetically different offspring

22. Genetic diversity Asexual Reproduction
Low genetic diversity with a high rate of reproduction
Disadvantage for adaptive purposes
Examples: Budding, Fragmentation, Fission
Organisms: Hydra, Bacteria

24. Sexual Reproduction
Many different possible gene combinations
Allows for diversity to be the foundation for evolution

25. Haploid life cycles Starting cells: haploid
Haploid individuals produce gametes through meiosis
Fusion: gametes come together to produce a diploid zygote
Diploid zygote will proceed through a type of diploid life cycle to correct genetic damage

26. Diploid life cycles Genetic information is from two parents
Production of gametes is produced through meiosis rather than mitosis
Fertilization: joining of a sperm and egg to produce an zygote
Zygote: a diploid cell

28. Alternation of Generations
Plants, algae and protists usually alternate between haploid and diploid cycles – very complex
Plants in Diploid Phase:
Sporophyte: cells within go through meiosis to produce spores
Spores: growth of an adult without fusion
Plants in Haploid Phase:
Gametophyte: production of gametes through mitosis – which must fuse to become adult