1. is derived from the Greek word meion, which means to reduce. Meiosis - is derived from the Greek word meion, which means to reduce.

2. 6.1 - Meiosis Meiosis is an important aspect of sexual reproduction (2 parents; offspring not genetically identical) The process of meiosis also shuffles genetic information (DNA) and results in variation in genes. Therefore producing a variation in offspring

3. Diploid, Haploid & Chromosomes  Normal body cells have a diploid (2n) chromosome number, meaning chromosomes occur in pairs (46 chromosomes).  In humans, the male and female each contribute half (haploid (n)), 23 chromosomes.

4. Gametes & Fertilization  Gametes – specialized cells necessary for reproduction Females – egg, Males – sperm  When fertilization takes place: 23 (egg,) + 23 (sperm) = 46 (zygote) The zygote goes on to develop into an embryo, and on into a complete individual.

5. Meiosis 46 chromosomes 23 chromosomes 23 chromosome 23 Chromosomes  occurs in reproductive organs and only produce gametes with half the chromosome compared to body cells 23 pairs, 46 chromosomes 23 Chromosomes

6. Meiosis I - Homologous Pair Separate Prophase I - Homologous chromosomes pair up, and non-sister chromatids exchange genetic material. This process is called crossing over. Metaphase I - Homologous chromosomes pair up at the equator. (one chromosome from each parent) Anaphase I - Homologous chromosomes separate and are pulled to opposite poles by the spindle fibres. (sister chromatids move to opposite poles ) Telophase I - One chromosome from each homologous pair is at each pole of the cell. Interkinesis - results in 2 daughter cells with ½ # of chromosomes. This stage between cell divisions the cell will grow and make proteins as in interphase of mitosis. Unlike interphase in mitosis, there is no replication of DNA during this stage.

7. Crossing over Is when sister chromatids exchange DNA during the Prophase Crossing over creates a number of genetic variations in gametes

8. Independent Assortment  A shuffling of the 23 homologous pairs, in which there are two possibilities for how chromosomes will sort themselves into daughter cells.  “independent assortment” leads to variations in species as there are more than 8 million combinations possible for the 23 pairs in any egg or sperm cell.  70 trillion different zygotes are possible from one sperm and one egg cell.

9. Meiosis II  Meiosis II is like mitosis because in both processes the chromatids of each chromosome are pulled to opposite poles.  Each daughter cell inherits one chromatid from each chromosome resulting in four haploid cells each with half the N of chromosomes. - Separates sister chromatids Prophase II - There is one chromosome of the homologous pair in each cell. Metaphase II - The X-shaped chromosomes form a single line across the middle of the cell. Anaphase II - Sister chromatids move to opposite poles of the cell. Once they separate, each sister chromatid is considered to be a chromosome. Telophase II - Spindle fibres begin to disappear, and a nuclear membrane forms around each set of chromosomes. Cytokinesis - In cytokinesis, the two daughter cells are separated.

10. Male and Female Gametes  In males, all 4 cells resulting from meiosis develop into sperm  In females, 1 cell gets most of the cytoplasm and becomes the egg while other 3 die, due to unequal cytoplasm and organelles

11. Differences in Mitosis and Meiosis Mitosis  # daughter chromosomes = # parent chromosomes  Two identical daughter cells  Occurs in all cells except reproductive cells  Produces diploid cells  Diploid cells = 2n Meiosis  # daughter chromosomes = half the # parent chromosomes  Four non-identical daughter cells  Occurs only in reproductive cells  Produces haploid cells  Haploid cells = n Review of Mitosis vs. Meiosis Comparison animation

13. Chromosome Mutation

14. Chromosome Mutations Sometimes occur spontaneously Chromosome changes during meiosis can cause changes in the genetic information. Occur because of mutagens Chromosome changes, sometimes leading to genetic disease or death, can be cause by mutagens such as radiation or chemicals Can occur if there is failed separation of chromosomes in meiosis Failed separation means that a gamete may end up with no chromosome or too many of a chromosome - Zygotes that result from these gametes rarely survive, and if they do, they will have serious genetic disorders Types: inverted, deleted, duplicated or moved to another spot

15. Genetic Disorders By using a karyotype, geneticists can study an individual’s chromosomes Chromosomes are identified and paired by size, centromere location and banding patterns. Certain genetic disorders or syndromes occur when there are specific chromosomes extra or missing Down syndrome usually occurs when there is an extra 21 st chromosome

16. Sexual Reproduction Chapter 6.2 (18 Ways to make a baby)

18. Sexual reproduction brings non-identical gametes together to form a new organism - it occurs in 3 stages:  Mating - the process by which gametes are brought together at same place and same time  Fertilization - process by which egg and sperm join to form a new organism (zygote)  Development - the process by which an organism develops as an embryo

19. Methods of Fertilization External or Internal Fertilization  In order for either of these methods to produce a successfully developing embryo, certain conditions must be met: 1. enough nutrients. 2. temperature must not be too cold or too hot. 3. Proper moisture so that embryo does not dry out. 4. protected from predators and items in environment that can potentially harm it.

20. External Fertilization  In external fertilization, sperm and egg join outside parents Advantages  Very little energy required to mate  Large numbers of offspring produced  Offspring can be spread widely in the environment - less competition between each other and parents Disadvantages  Many gametes will not survive  Many eggs will not be fertilized  Offspring are often not protected by parents, so many of them die Frog Eggs

21. External Fertilization Example

22. Internal Fertilization  In internal fertilization, sperm and egg join inside parents, embryo is nourished inside mother Advantages  Embryo protected from predators  Offspring more likely to survive, as many species will protect their young while they mature Disadvantages  Much more energy required to find mate  Fewer zygotes produced, resulting in fewer offspring  More energy required to raise and care for offspring

23. Pollination  Most plants transfer male gametes as pollen. Pollen can be carried by wind or other organisms.

24. Human Reproductive System  Once ovulated, the egg is only viable for about 24 hours if not fertilized.  Fertilization occurs in the top one third of the Fallopian tubes.  After fertilization, the zygote continues to move down the fallopian tube.  As it does, development begins.  It takes the embryo 7 - 12 days to get to the uterus and implant in the endometrium.

25. Embryonic Development  Embryonic development is the early development of an organism - in humans, it is the first three months after fertilization Stages  End of the first week - ball of cells called morula  By end of second week it is a hollow ball called a blastula Cells at this stage are stem cells, and have the ability to develop into any kind of cell  3-4 weeks embryo is known as a gastrulagastrula develops 3layers: ectoderm (skin, nerves), mesoderm (muscles, bones), and endoderm (lungs, liver, digestive system lining)  “more blasting gas”

26. Gastrula

27. Embryonic Development Period of the Embryo  For the first three months, organogenesis occurs and it is termed an embryo.  This is a 6 week embryo.

28. Can you guess which embryos are: chicken, fish, human, rabbit, salamander, and tortoise

29. Fetal Development  The cell layers now differentiate into the organs and tissues of a baby - this is divided into 3 trimesters. First Trimester (0-12 weeks)  Organ systems begin to develop and form. Bone cells form. Second Trimester (12-24 weeks)  Rapid growth from 12-16 weeks. Third Trimester (24+ weeks)  Continued growth, especially of brain. Fat begins to deposit at 32 weeks to keep baby warm at birth.

30. This is a 4 month fetus.  The third trimester, period of the baby, is marked by growth and maturation of all organs and organ systems.  The baby is capable of life outside the womb during this period.

31. Review: Life cycle of animals

32. Sexual Reproduction: Advantages and Disadvantages

33. 6.3 Assisted Reproductive Technologies  Infertility is the inability of a couple to have a baby  Assisted reproductive technologies involve removing eggs from the woman, fertilizing them, and returning them to the uterus.  Reproductive technologies help childless couples, but carry a higher risk of birth defects. Also creates the problem of “unwanted” embryos. What should be done with them?

34. Types of Assisted Reproductive Technologies 1. Artificial Insemination - donor sperm is placed in the female. 2. In vitro fertilization (IVF) - egg and sperm are collected and fertilization takes place in a dish. Embryo(s) then placed in female’s uterus. 3. Gamete intrafallopian transfer (GIFT) - eggs and sperm are collected, mixed, then injected into the woman’s fallopian tubes. 4. Intracytoplasmic Sperm Injection (ICSI) - a single sperm is injected directly into an egg.