Chapter 8

1. Chapter 8 Cell Reproduction http://biofinity.org/images/Cell%20Division%20Micrograph.jpg

2. Section 1 Vocabulary Pretest • Chromosome • Histone • Chromatid • Centromere • Chromatin • Sex Chromosome • Autosome • Homologous Chromosome • Karyotype • Diploid • Haploid • Cells with one set of chromosomes • Cells with two sets of chromosomes • Rod-shaped structures made of DNA and proteins • Proteins found in DNA • X and Y chromosomes • A chromosome other than a sex chromosome • All chromosomes visible in a cell • Matching chromosomes • Copied half of a chromosome • Holds chromatids together • DNA during interphase

3. Answer Key Chromosome C Histone D Chromatid I Centromere J Chromatin K Sex Chromosome E Autosome F Homologous Chromosome H Karyotype G Diploid B Haploid A

4. Why Cells Divide http://stealthisknowledge.com/Pictures/images-mesoblast_cell_division_still.jpg Growth and repair Creation of gametes (Sex Cells) Method of reproduction in unicellular organisms

5. Chromatin http://kmarsh2.umwblogs.org/files/2008/10/mitosis_cartoon_1.jpg While cells are growing, their DNA appears as long, stringy chromatinmaterial. When cells are ready to divide, the chromatin condenses to form chromosomes.

6. Chromosomes Histones http://activity.ntsec.gov.tw/lifeworld/english/content/images/en_gene_c5.jpg • Chromosomes —DNA wrapped around proteins to form an X-shaped structure • Histones —proteins that DNA wraps around • Sections of chromosomes are called genes • http://www.youtube.com/watch?v=9kQpYdCnU14

7. Chromosome Structure http://www.biologycorner.com/resources/chromosome-labeled.gif Each chromosome is made of two identical halves called sister chromatids held together at a point called a centromere. The sister chromatids are the result of DNA copying itself. They are called double stranded and will need to separate before the cell divides.

8. Chromosome Numbers • Humans have 46 chromosomes in the nucleus of every cell • Two are the sex chromosomes (X and Y) • XX = female • XY = male • The other 44 are called autosomes • They occur in matching pairs • Called homologous chromosome pairs • One chromosome in each pair comes from mom and the other comes from dad

9. Karyotypes http://www.mathemagic.org/MOBM/images/karyotype.jpg A karyotype is a photograph of the matching pairs of chromosomes http://www.youtube.com/watch?v=V8sNC9Cdv0E&feature=related

10. Diploid vs Haploid • Diploid cells contain the full set of chromosomes (all 46) • All body cells are diploid • Haploid cells contain half the number of chromosomes (23) • One from each homologous pair • Sperm and egg cells are haploid

11. Section 2 Vocabulary Pretest • Binary fission • Mitosis • Asexual reproduction • Meiosis • Gametes • Interphase • Cytokinesis • Prophase • Spindle fiber • Metaphase • Anaphase • Telophase • Cell plate • Division of cell’s cytoplasm • Division of cell’s nucleus • Reproductive cells • Division of a prokaryotic cell • Pull chromatids apart • Chromosomes line up in middle of the cell • Chromatids separate • Two new nuclei form • Production of offspring from one parent • Time between cell divisions • Results in the formation of gametes • First phase of mitosis • Forms between two new plant cells

12. Answer Key Binary fission D Mitosis B Asexual reproduction I Meiosis K Gametes C Interphase J Cytokinesis A Prophase L Spindle fiber E Metaphase F Anaphase G Telophase H Cell plate M

13. Cell Division • http://www.youtube.com/watch?v=Q6ucKWIIFmg • How many new cells do you make every day? • About 2 trillion (25 million cell per second) • Cells reproduce asexually (one parent) • One cell becomes two • The process is different in prokaryotes and eukaryotes

14. Cell Division in Prokaryotes • Prokaryotes reproduce by binary fission • DNA is circular (no chromosomes) • DNA copies itself • Cell divides---Simple 

15. Cell Division in Eukaryotes http://ghr.nlm.nih.gov/handbook/illustrations/mitosismeiosis.jpg • Eukaryotes use two types of cell division • Mitosis —produces body cells • Meiosis—produces gamete cells • Both mitosis and meiosis happen in stages

16. The Cell Cycle http://faculty.capebretonu.ca/cglogowski/BIOL%20101%20IMAGES/CellCycle_L.jpg • Mitosis is part of the Cell Cycle • Three stages in the Cell Cycle: • Interphase —period of growth, development and DNA replication • Mitosis —division of the nucleus • Cytokinesis —division of the cytoplasm • http://www.youtube.com/watch?v=lf9rcqifx34&feature=related

17. Interphase http://imcurious.wikispaces.com/file/view/cell_cycle.jpg/114427989/cell_cycle.jpg • Cells spend most of their time in interphase • Three phases • G1—first growth phase (Cells grow to full size) • S—DNA synthesis (copied) • G2—second growth phase (prepares to divide)

18. Some cells exit the cycle after the G1 phase and enter the G0 phase. These cells no longer divide. • Muscle cells • Nerve cells

19. Mitosis • Mitosis (division of nucleus) is divided into four stages: • Prophase • DNA condenses into chromosomes • Nuclear membrane disappears • Centrioles and spindle fibers appear • Metaphase • Chromosomes line up in the middle of the cell • Anaphase • Sister chromatids separate and move toward poles • Telophase • Chromosomes uncoil back into chromatin • Nuclear membrane forms around each set of chromosomes

20. Stages of Mitosis Interphase Prophase Metaphase Anaphase Telophase http://www.clt.astate.edu/mhuss/mitosis1.jpg

21. Cytokinesis http://www.uic.edu/classes/bios/bios100/lectf03am/cleavage.jpg http://www.vcbio.science.ru.nl/images/cellcycle/mito_solanum_cellplate.jpg • The final stage of the cell cycle is cytokinesis (dividing the cytoplasm) • In animal cells, cytokinesis begins with a pinching in of the membrane forming a cleavage furrow. • In plant cells, cytokinesis begins with the formation of a cell plate. • End result is two identical diploid daughter cells

22. Meiosis • Meiosis produces gamete cells (sperm and egg cells) • Gamete cells are haploid (half the number of chromosomes) • Full number of chromosomes is restored during fertilization. • A cell passes through interphase and copies its DNA. • The cell then divides twice resulting in 4 haploid gamete cells.

23. http://www.biologycorner.com/resources/crossingover.jpg • Meiosis is also divided into stages: • Prophase I • Chromosomes form and find their homologous match • This is called synapsis (pairing of homologous chromosomes) • Each pair of homologous chromosomes is called a tetrad. • Crossing over can occur in each tetrad resulting in a genetic recombination of genes.

24. X diploid • Metaphase I • Matching pairs of chromosomes (tetrads) line up in the middle of the cell and attach to spindle fibers. • Anaphase I • Homologous chromosomes separate and move to the poles (independent assortment) • Telophase I and Cytokinesis I • Nucleus and Cell both divide for the first time. This reduces the number of chromosomes to one half. This is called a reduction division. • However, the chromosomes are still double stranded.

25. Prophase II • Spindle fibers reappear • Metaphase II • Chromosomes line up in the middle of the cell and attach to spindle fibers • Anaphase II • Chromatids split and move to poles • Telophase II and Cytokinesis II • Nucleus and cell divide for the second time • This is essentially a mitotic division. • 4 haploid gamete cells are produced. They have half the number of single stranded chromosomes.

26. http://www.phschool.com/science/biology_place/labbench/lab3/images/stages2.gifhttp://www.phschool.com/science/biology_place/labbench/lab3/images/stages2.gif

27. Meiosis occurs in the testes and the ovaries Spermatogenesis —production of 4 mature sperm cells. Oogenesis —production of 1 mature egg cell and 3 smaller polar bodies that degenerate. http://www.biologycorner.com/resources/oogenesis.jpg

28. Fertilization http://biology.ucsd.edu/classes/bimm110.SP07/images/fertilization2.jpg Fertilization —union of sperm and egg cell. Sexual reproduction, involving the production of sperm and egg cells by meiosis followed by fertilization, ensures genetic variation in all offspring.