1 / 17

Meiosis

Meiosis. Homologous Chromosomes. Homologous chromosomes : pairs of chromosomes with genes for the same traits, but they can have different information about those traits. ½ the chromosomes in a cell come from Mom, ½ the chromosomes in a cell come from Dad. The Homolog’s. Humans.

marv
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

  2. Homologous Chromosomes • Homologous chromosomes: pairs of chromosomes with genes for the same traits, but they can have different information about those traits • ½ the chromosomes in a cell come from Mom, ½ the chromosomes in a cell come from Dad

  3. The Homolog’s

  4. Humans • Humans have 46 chromosomes or 23 pairs of homologous chromosomes. • Somatic(body) cells contain 46 chromosomes. • 46 is the diploid (2N) number for humans. - Diploid means that a cell has both homologs for each chromosome • Somatic cells reproduce by mitosis

  5. Reproductive Cells • Gametes(eggs and sperm) are called haploid (N)because they contain one set of chromosomes. • Eggs (Ovum)and sperm contain 23 chromosomes. • Eggs and sperm are produced by meiosis- a process that reduces chromosomes by half

  6. Phases of Meiosis • Meiosis is a process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosome in a diploid cell. • Two steps • Meiosis I and Meiosis II • One diploid cell gives rise to 4 haploid cells

  7. Who does it? • Plants • Fungi • Animals (including you) • Males start meiosis at puberty. • Females start meiosis in utero.

  8. Where does it occur? • In your gonads • Females- the ovary • Males-the testicles

  9. Why does it occur? • Genetic Variation • Mixes genes from Mom and Dad to create a unique baby • Reduce the chromosome number by half • Ensures that each cell produced has one copy from each homologous pair of chromosomes • 23 in sperm + 23 in egg unite (fertilization) leads to a 46 zygote(baby)

  10. Meiosis I • Prior to this phase, each chromosome is replicated • Then its looks a lot like Mitosis with 4 phases • Prophase I • Metaphase I • Anaphase I • Telophase I and Cytokinesis • The major difference is what happens in Prophase I

  11. Prophase I • Homologous chromosomes join to form a tetrad • Chromosomes in the tetrad exchange portions of themselves in process known as crossing-over

  12. Crossing-over • Results in new genetic combinations - It is another way to increase genetic diversity

  13. The rest of Meiosis I looks the same as Mitosis except • The two new cells have sets of chromosomes and alleles that are different from each other and from the diploid cell that enter meiosis I

  14. Meiosis II • This time no chromosome replication occurs before entering prophase II. • Again it looks similar to Mitosis but now we have a separation of the chromosomes • Resulting in four new cells with half number of chromosomes (haploid cells)

  15. Gametes 2N = 4 Metaphase II Telophase I Anaphase II Anaphase I Interphase I Metaphase I N=2 Prophase I N = Number of Chromosomes

  16. Comparing Mitosis and Meiosis • Mitosis results in the production of two genetically identical diploid cells. • Allows an organism to grow, reproduce, and replace cells. • Meiosis results in the production of four genetically different haploid cells. • Allows organisms to reproduce sexually

More Related