1 / 16

SPECIALIZED SEX CELLS

SPECIALIZED SEX CELLS. WHY ARE THEY NECESSARY?. 4n = 92 too many. Why do diploid organisms need to have specialized sex cells?. Sex cells (gametes: sperm or egg) allow traits to be combined from two organisms. 2n (46). 2n (46). +. Diploid cells (2n) Gametes (n) . 2n = 46.

abril
Download Presentation

SPECIALIZED SEX CELLS

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. SPECIALIZED SEX CELLS WHY ARE THEY NECESSARY?

  2. 4n = 92 too many Why do diploid organisms need to have specialized sex cells? • Sex cells (gametes: sperm or egg) allow traits to be combined from two organisms 2n (46) 2n (46) +

  3. Diploid cells (2n) Gametes(n) 2n = 46 Sexual Reproduction • Gametes have only one of each chromosome • Requires special cell division: Meiosis • Takes place in gonads (testis, ovary) n (23) n (23) +

  4. How is Meiosis different from Mitosis? Meiosis Cells divide 2x Mitosis Cells divide 1x 2n 2n 2n 2n n n Diploid Cells n n n n Haploid Cells

  5. Different cells Mitosis Meiosis Identical cells

  6. Mitosis Meiosis Cells divide again; sister chromatids line up Cell division is over Done

  7. How many unique gametes can a cell with two pairs of chromosomes make?

  8. Why bother? • (2)23 > 8 million different possible gametes • For humans with 23 pairs of chromosomes? • For a couple • possible unique offspring • (8 million) x (8 million) = (64,000,000,000,000) But wait! There’s more!

  9. Crossing over enables even greater variety • Exchange of equivalent sections between homologous chromosomes. • Occurs at random locations along chromosome. • Creates new versions of chromosomes.

  10. CQ#1: The cell to the right shows a diploid organism with two chromosomes (2n=2). The pictures below show some of the steps this cell may go through during mitosis or meiosis. A. B. C. D. E. F. G. H. Place the appropriate steps in order for a cell going through mitosis. (Note: you may use just some or all of the steps.)

  11. CQ#2: The cell to the right shows a diploid organism with two chromosomes (2n=2). The pictures below show some of the steps this cell may go through during mitosis or meiosis. A. B. C. D. E. F. G. H. Place the appropriate steps in order for a cell going through meiosis. (Note: you may use just some or all of the steps.)

  12. Parent #2 Parent #1 CQ#3: The different copies of chromosome 21 in John and Jane are shown to the right. Which of the following is a normal gamete that might be produced by either John or Jane? A B C D E

  13. KING HENRY VIII • King Henry married six times in hopes of producing a strong line with male heirs. • Katherine of Aragon • Anne Boleyn • Jane Seymour • Anne of Cleves • Katherine Howard • Katherine Parr

  14. CHILDREN • Katherine of Aragon had six pregnancies: 3 sons, 3 daughters, only one daughter survived • Anne Boleyn had three pregnancies: 1 son, 1 daughter, and 1 unknown, only 1 daughter survived. • Jane Seymour had one pregnancy: 1 son, who survived • None of Henry’s remaining wives had pregnancies

  15. WHO WAS AT FAULT? • Henry divorced Katherine, and beheaded Anne due to his belief that his wives were denying him male heirs. • CQ#4: Was it in fact the fault of his wives? YES NO

  16. WHY? • Females can provide only X’s to their children • Males can provide either an X or a Y

More Related