1 / 28

Chapter 10 Sexual Reproduction & Genetics

Chapter 10 Sexual Reproduction & Genetics. Part 1: Meiosis. Concepts for Review. Chromatin is the relaxed form of DNA Chromosome is the coiled form of DNA Sister chromatids are identical copies of DNA (after S-phase/replication). Key Terms .

sahirah
Télécharger la présentation

Chapter 10 Sexual Reproduction & Genetics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 10 Sexual Reproduction & Genetics Part 1: Meiosis

  2. Concepts for Review • Chromatin is the relaxed form of DNA • Chromosome is the coiled form of DNA • Sister chromatids are identical copies of DNA (after S-phase/replication)

  3. Key Terms • Homologous chromosomes are chromosomes that make up a pair, one from each parent • Not necessarily identical but… • Are the same length • Have the same genes

  4. Key Terms • Diploid refers to complete chromosome sets in a cell (or 2N) • N= the number of chromosomes in a gamete (sex cell) • N chromosomes from the female parent + N chromosomes from the male parent= 2N • For humans, 2N = 46

  5. Key Terms • Haploid refers to single chromosomes in a cell (or N) • One-half of the 2N set (the maternal N or the paternal N) • Gametes (i.e. sperm, egg sex cells) are haploid cells • For humans, N = 23

  6. Bottom Line • diploid means that there are the full number of chromosomes where as haploid means that there are half the number of chromosomes.

  7. Key Terms • Meiosis is a type of cell division that reduces the number of chromosomes • Forms gametes (i.e. sex cells) • Occurs in the reproductive structures of organisms that reproduce sexually • Occurs in 2 consecutive cell divisions: meiosis I and meiosis II

  8. Before meiosis Interphase occurs…. • Replication of DNA occurs. • Chromosomes Condense Sounds familiar right???

  9. Reducing 2N cells to… Meiosis I: “Reduction Division” N cells

  10. PROPHASE I • Homologous chromosomes pair up • Crossing over occurs • Nuclear envelope breaks down • Spindles form

  11. Crossing Over • Chromosomal segments (genetic information) are exchanged between a pair of homologous chromosomes

  12. METAPHASE I • Spindle fibers attach to the centromeres • Homologous Chromosomes Line up at the equator

  13. ANAPHASE I • Homologous chromosomes separate and move to the opposite poles of the cell

  14. TELOPHASE I • The cell divides • The result is two daughter cells. • Each daughter cell is haploid. • The daughter cells are not genetically identical **During Telophase I Cytokinesis occurs at the same time!!**

  15. Meiosis II: “Mitotic Division” Separating sister chromatids

  16. Nucleus breaks up • Spindles form and attach to centromere

  17. Sister chromatids randomly align at middle of cell

  18. Sister chromatids separate • Chromosomes move to opposite poles of cell

  19. Cells divide • 4 haploid daughter cells result • Each cell is genetically different

  20. Summary of Key Concepts • Chromosomes contain genes (humans have 46 chromosomes or 23 homologous pair) • Homologous chromosomes may contain different forms of the same genes • Meiosis reduces chromosome # by ½ and results in sex cells (gametes) • Crossing-over increasing genetic variation Click here for detailed animation of meiosis

  21. which set of chromatids illustrates the result of a single crossover of the homologous chromosomes?

More Related