1 / 19

Meiosis

Meiosis. Pgs. 96-100. Sexual Reproduction and Genetics. Meiosis - General Overview. Human body cells have 46 chromosomes. Each parent contributes 23 chromosomes. Takes place in sex cells (gametes): egg and sperm One cell becomes 4 NON-IDENTICLE cells. Sexual Reproduction and Genetics.

baina
Download Presentation

Meiosis

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. Meiosis • Pgs. 96-100

  2. Sexual Reproduction and Genetics Meiosis - General Overview • Human body cells have 46 chromosomes • Each parent contributes 23 chromosomes • Takes place in sex cells (gametes): egg and sperm • One cell becomes 4 NON-IDENTICLE cells

  3. Sexual Reproduction and Genetics Meiosis – Homologous Chromosomes Chromosomes and Chromosome Number • Same length • Same centromere position • Carry genes that control the same inherited traits • One is from mother, one is from father = a matching set

  4. Sexual Reproduction and Genetics Meiosis Haploid and Diploid Cells • An organism produces gametes to maintain the same number of chromosomes from generation to generation. • Human gametes contain 23 chromosomes. • A cell with n chromosomes is called a haploid cell. • A cell that contains 2n chromosomes is called a diploid cell.

  5. Sexual Reproduction and Genetics • When gametes combine in fertilization, the number of chromosomes is restored. Meiosis Meiosis I • The sexual life cycle in animals involves meiosis. • Meiosis produces gametes.

  6. Sexual Reproduction and Genetics Meiosis Meiosis I • Interphase • Chromosomes replicate. • Chromatin condenses. Interphase

  7. Sexual Reproduction and Genetics Meiosis Meiosis I • Prophase I • Pairing of homologous chromosomes occurs. • Each chromosome consists of two chromatids. Prophase I • The nuclear membrane breaks down. • Spindles form.

  8. Sexual Reproduction and Genetics Meiosis Meiosis I • Prophase I • Crossing over produces exchange of genetic information. • Crossing over—chromosomal segments are exchanged between a pair of homologous chromosomes.

  9. Sexual Reproduction and Genetics Meiosis Meiosis I • Metaphase I • Chromosome centromeres attach to spindle fibers. Metaphase I • Homologous chromosomes line up at the equator.

  10. Sexual Reproduction and Genetics • Homologous chromosomes separate and move to opposite poles of the cell. Meiosis Meiosis I • Anaphase I Anaphase I

  11. Sexual Reproduction and Genetics Meiosis Meiosis I • Telophase I • The spindles break down. Telophase I • Chromosomes uncoil and form two nuclei. • The cell divides.

  12. Sexual Reproduction and Genetics • A second set of phases begins as the spindle apparatus forms and the chromosomes condense. Meiosis Meiosis II • Prophase II Prophase II

  13. Sexual Reproduction and Genetics • A haploid number of chromosomes line up at the equator. Meiosis Meiosis II • Metaphase II Metaphase II

  14. Sexual Reproduction and Genetics • The sister chromatids are pulled apart at the centromere by spindle fibers and move toward the opposite poles of the cell. Meiosis Meiosis II • Anaphase II Anaphase II

  15. Sexual Reproduction and Genetics • The chromosomes reach the poles, and the nuclear membrane and nuclei reform. Meiosis Meiosis II • Telophase II Telophase II

  16. Sexual Reproduction and Genetics Meiosis Meiosis II • Cytokinesis results in four haploid cells, each with n number of chromosomes. Cytokinesis

  17. Sexual Reproduction and Genetics Meiosis The Importance of Meiosis • Meiosis consists of two sets of divisions • Produces four haploid daughter cells that are not identical • Results in genetic variation

  18. Sexual Reproduction and Genetics Meiosis Meiosis Provides Variation • Depending on how the chromosomes line up at the equator, four gametes with four different combinations of chromosomes can result. • Genetic variation also is produced during crossing over and during fertilization, when gametes randomly combine.

  19. Mitosis vs Meiosis

More Related