1 / 13

Ways to show the number of chromosomes in a cell.

DIPLOID. HAPLOID. n 1 copy of each chromosome Sex cells. 2n 2 copies of each chromosome Body cells. Ways to show the number of chromosomes in a cell. n. Definition: Cell division where cells divide twice. Done by:

jeromeshaw
Télécharger la présentation

Ways to show the number of chromosomes in a cell.

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. DIPLOID HAPLOID • n • 1 copy of each • chromosome • Sex cells • 2n • 2 copies of each • chromosome • Body cells Ways to show the number of chromosomes in a cell.

  2. n Definition: Cell division where cells divide twice. Done by: Sex cells in multi-cellular organisms (diploid) Meiosis Variation: Crossing over – genes switch between homologs. Independent assortment – homologous chromosomes line up differently every time. Mutations Sexual reproduction Results in: 4 cells with ½ DNA (haploid cells) 2n Zygote (baby) n + =

  3. What Happens During Meiosis?

  4. MEIOSIS I • A diploid (2N) cell divides to produce 2 daughter cells. • Creates genetic variation.

  5. Prophase I • Homologous chromosomes pair up to form tetrads (groups of four chromatids). • Crossing over occurs when homologous chromosomes overlap.

  6. Metaphase I • Tetrads line up at the center of the cell.

  7. Anaphase I • One homologous chromosome is pulled to each side of the cell.

  8. Telophase I • Two daughter nuclei are formed. • Followed by cytokinesis and then immediately meiosis II. • NO replication!

  9. MEIOSIS II • Two cells each divide to form four haploid (N) gametes. • In females, one viable egg + three “polar bodies” • In males, four viable sperm

  10. Prophase II • Chromosomes condense in each cell.

  11. Metaphase II • In each cell, chromosomes line up in the middle.

  12. Anaphase II • In each cell, sister chromatids are pulled apart.

  13. Telophase II • 4 new nuclei form, 2 in each cell. • Followed by cytokinesis, resulting in 4 haploid (N) gametes.

More Related