Unit 4: Reproduction Chapter 6

1. Unit 4: ReproductionChapter 6 Meiosis is the basis of sexual reproduction.

2. Mitosis Recap https://www.youtube.com/watch?v=JayldCyv5eQ

3. Sexual Reproduction Section 6.1: Meiosis • Sexual Reproduction: a method of reproduction involving two parents, producing offspring that are genetically different from each other, either parent, and from other members of their species.

4. The Process of Sexual Reproduction • Sexual reproduction involves uniting specialized cells called Gametes. In animals, male gametes are called sperm and female gametes are called eggs. • Fertilization occurs when the gametes unite, with the sperm penetrating an egg cell. • The process of fertilization results in a cell called a Zygote. The Zygote undergoes cell division and mitosis and develops into an Embryo. The embryo grows continuously to form a new organism.

5. Chromosome Numbers • Diploid number (2n): body cells (all cells excluding sperm and egg) have two sets of chromosomes. The diploid number for humans is 46 (2 x 23). Humans inherit one set of 23 from their male parent and one set of 23 from their female parent. • Haploid number (n): gametes (sperm and egg cells) have only one set of chromosomes and are termed haploid. Human gametes have one set of 23 chromosomes. So, the haploid number for humans is 23. • During fertilization, a haploid (n) sperm cell unites with a haploid (n) egg cell to form a diploid (2n) zygote. https://www.youtube.com/watch?v=BAOFVwQj1yg

6. Meiosis • Meiosis: process of producing gametes (sperm and egg cells) with the haploid (n) number of chromosomes. Meiosis occurs in the male and female sex organs (respectively the testes and ovaries).

7. Meiosis • Meiosis involves two rounds of cellular division: • Meiosis I • Meiosis II

8. Homologous Chromosomes • Homologous Chromosomes: are pairs of chromosomes that are the same size, shape and have genes that are in the same locations.

9. Meiosis I: Stages • Meiosis I involves: • Prophase I • Metaphase I • Anaphase I • Telophase I

10. Prophase I • Homologous chromosomes pair up.

11. Metaphase I • Homologous chromosomes pair up at the equator.

12. Anaphase I • Homologous chromosomes separate and are pulled towards opposite poles (ends) of the cell.

13. Telophase I • Homologous pairs have moved to opposite ends of the cell and the cell begins to divide.

14. Interkenesis • Interkenesis: is the stage between cell divisions. The cells grow and make various proteins.

15. End Products of Meiosis I • The end products of Meiosis I are two diploid (2n) daughter cells. • These cells now go on to enter Meiosis II.

16. Meiosis II • Meiosis II involves: • Prophase II • Metaphase II • Anaphase II • Telophase II

17. Prophase II • There is one chromosome of the homologous pair in each cell.

18. Metaphase II • Chromosomes line up at the equator (middle of the cell).

19. Anaphase II • Half of each X-shaped chromosome is pulled apart towards opposite poles (ends) of the cell.

20. Telophase II • A nucleus forms around each set of chromosomes and the cell begins to divide to produce 4 gametes.

21. Comparing/ContrastingMitosis verses Meiosis

22. Meiosis Video • https://www.youtube.com/watch?v=AdfrH3J5Cwc

23. Section 6.2: Sexual Reproduction • Sexual reproduction involves two parents. • Sexual Reproduction does not necessarily require sexual intercourse.

24. Method of Fertilization • Fertilization may be: • Internal Fertilization – sperm cells are deposited inside the female’s body where they meet an egg cell. Requires sexual intercourse. • External Fertilization- sperm and egg cell unite outside the bodies of parents. This is common in animals that live in water.

25. Organisms that reproduce sexually • Mosses • External fertilization occurs in mosses. • Water is needed to transport gametes, allowing sperm cells and egg cells to unite. • Male and female sex organs develop on the end of stems or branches. • Asexual reproduction may also occur by spore production.

26. Organisms that reproduce sexually • Flowering Plants • Internal fertilization occurs in flowering plants. • The process of Pollination occurs. Male gametes are formed in special cases called Pollen. Pollination is the transfer of pollen to the female part of the flower. • The male reproductive organ in a flower is called the Stamen. The female reproductive organ in a flower is called the Pistil. • Pollination and fertilization occurs at the female reproductive organ, at the pistil. The pollen lands on the pistil and sperm are delivered to the egg cells. The fertilized egg becomes a seed. The seed protects the developing embryo.

27. Organisms that reproduce sexually • Insects • The life cycle of insects involves metamorphosis. Metamorphosis is the change in an individual's form as it develops.

28. Incomplete Metamorphosis • Incomplete Metamorphosis: involves subtle (minor) changes through 3 life cycle stages: • Egg • Nymph (smaller immature version of adult) • Adult Grasshoppers go through Incomplete Metamorphosis. https://www.youtube.com/watch?v=lXV6B7qnnmg

29. Complete Metamorphosis • Complete Metamorphosis: a change in the form of an insect as it matures, where the adult is completely different than the larval stage. • The four common stages of complete metamorphosis, as seen in the butterfly are: • Egg • Larva (caterpillar) • Pupa • Adult https://www.youtube.com/watch?v=Am0aq8SYeio

30. Asexual verses Sexual Reproduction

31. Section 6.4: Studying Genetic Changes • Genetic conditions that cannot be solved using current scientific & technological knowledge include: • Down Syndrome • Result of an extra 21st chromosome • Individuals have characteristic facial features and a shorter stature. They may be prone to heart defects and other diseases such as Alzheimer’s and leukemia.

32. Genetic Conditions • Allderdice Syndrome • Unique to Sandy Point, NL. • An increase in genetic birth defects was noticed due to geographic isolation. • Result of a mutation on a single maternal chromosome. • 31% chance of developing the syndrome.

33. Genetic Conditions 3. Cystic Fibrosis • Chronic disease that causes all bodily mucous to become thick, sticky and difficult to expel. • Caused by a gene mutation on a single chromosome. An individual only needs one gene to prevent it but most people have two (one on each homologous chromosome). So the individual must inherit an absence of both genes to develop disease.

34. Shifts in the Field of Genetics • Our understanding of genetics has changed over time as new technologies have become available. New technologies have made it possible to get a better look at genes and their influence on traits.

35. Mendel’s Experiments • In the mid 1800’s, Gregor Mendel experimented with inherited traits in pea plants, including color and shape. • Mendel’s studies of pea plants demonstrated that traits were inherited from one generation to the next. • Mendel’s studies suggested the involvement of “dominant” and “recessive” factors in the transmission of traits from parents to offspring. Dominant traits are always expressed, however recessive traits are not always expressed.

36. Watson and Crick: The double helix model of DNA • A more clear understanding of genes came about when Francis Crick and James Watson, described the structure of DNA in 1953. • Crick and Watson showed that DNA is an organization of genes in a double helix shape, like a twisted ladder. Specific base pairing on this ladder helped to explain how DNA could replicate (copy itself). This development also helped to explain how and why mutations occur.

37. Human Genome Project • In the Human Genome Project, scientists around the world collaborated for about 20 years to identify every gene in human DNA, mapping the human genome. • The Human Genome Project made a sort of map that can be used to search for and identify particular genes. • The Human Genome Project has provided information into how and why various genetic diseases come about.

38. Genetic Engineering • Genetic Engineering: is biotechnology that deals with the manipulation of the genome. • Scientists have figured out how to cut a gene out of one DNA strand and place it into another. The ability to recombine DNA (recombinant DNA) has made significant contributions to food and medicine.

39. Genetic Engineering & Food Production • Plants and animals have improved through recombinant DNA technology. Such organisms are labeled as Genetically Modified Organisms (GMOs). This plays an important role in the agricultural industry, specifically crop production. • Genes have been altered to produce plants that are resistant to colder temperatures, chemicals and disease. • Genetic engineering has been used to produce organisms with desired traits.

40. Genetic Engineering & Medicine • Scientists use recombinant DNA technology to produce drugs and provide human gene therapy. • Recombinant DNA technology is being used to help Diabetes patients, in which the correct human gene for insulin production, is placed within the genome of a bacterium. The bacterium then produces insulin which can be used as medicine. • Humans who lack a specific gene or who have a defective gene can have a healthy, functioning gene inserted into their DNA. This is human gene therapy. • https://www.youtube.com/watch?v=_IgSDVD4QEc