Chapter 8- Cellular Reproduction and Development

1. Anaphase Anchorage dependence Asexual reproduction Autosomes Benign Binary fission Cancer cells Cell cycle Cell cycle control system Cell division Cell plate Centromeres Centrosomes Chiasma Chromatin Chromosomes Cleavage furrow Crossing over Cytokinesis Deletion Density-independent inhibition Diploid Downs syndrome Duplication Fertilization Gametes Genetic recombination Genome Growth factor Haploid Homologous chromosomes Interphase Inversion Karyotype Locus Malignant Meiosis Metaphase Metastasis Mitosis Mitotic phase (M phase) Mitotic spindles Nondisjuction Prophase Sex chromosomes Sexual reproduction Sister chromatids Somatic cell Telophase Translocation Trisomy Tumor Zygote Chapter 8- Cellular Reproduction and Development

2. What are the 2 types of reproduction? • Asexual- production of offspring by single organism • Inherit DNA from one parent • Offspring are identical to parent • Sexual- reproduction process involving union of sperm and egg • DNA is inherited from both parents • Offspring are a 50% match to each parents DNA • Produces GREAT variation

3. Chromatin / Chromosomes • Structure that contains most of the organism’s DNA • Chromatin coils up into chromosomes in preparation of cell division

4. Review: Cell Theory • Cells are the basic unit of structure and function • All organisms are comprised of cells • All cells come from pre-existing cells** • Cells produce new cells by cell division- to grow, develop and reproduce

5. Prokaryotes: • Divide by binary fission • Copied DNA moves to opposite sides of the cell and the cell then splits in two

6. Eukaryotes • DNA is packaged into chromosomes • Proteins help organize and package the DNA • Sister chromatids- two copies of 1 chromosome • Centromere- where chromatids are joined • During cell division- sister chromatids separate, after separation they are called chromosomes

7. The Cell Cycle

8. The Cell Cycle • Interphase (3 phases) • G1- increase protein supply, increase #’s of organelles, grows in size • S- DNA replication, single chromosomes duplicate to form two sister chromatids • G2- proteins that are essential for division are made

9. The Cell Cycle • M phase- (2 phases) • Mitosis- nucleus and its’ contents divide • Cytokinesis- cytoplasm is divided • Produces genetically identical daughter cells

10. Mitosis • For growth, replacement and asexual reproduction • 4 phases:

11. Mitosis

13. Prophase • Chromosomes are formed, nucleoli disappear, mitotic spindles begin to form, at the end- nuclear membrane breaks apart • Mitotic spindle- football shaped group of microtubules that guide chromosome separationg • Centrosome- where microtubules originate, containing centrioles • Kinetochore- protein by centromere, is where microtubules attach

14. Metaphase • Chromosomes line up along the metaphase plate

15. Anaphase • Centromeres come apart, sister chromatids separate, microtubules shorten and poles are moved farther apart, chromosomes move to opposite ends of the cell

16. Telophase & Cytokinesis • Telophase- daughter nuclei appear, nuclear membrane reforms, chromosomes uncoil, mitotic spindles disappear • Cytokinesis- • Animal- by process of cleavage -cleavage furrow, shallow groove at surface, ring of actin contracts and pinches cell in two • Plant- vesicles containing cell wall material collect in the middle of cell -vesicles fuse forming cell plate and it’s grows out, membrane of cell plate fuses with plasma membrane and cell wall

18. What affects the cell division? • Anchorage dependence- requirement that a cell must be anchored to something to divide, stops loose cells from dividing at an inappropriate time

19. What affects the cell cycle? • Density-dependent inhibition- cell division slow as population becomes denser • If cells are scraped off, cells bordering it will divide until space is again taken up • Growth factor- protein secreted by cells that stimulate others to divide • Most require it to start, and stop when it runs out

21. How is the cell cycle controlled? • Proteins trigger and control cell cycle events • Protein will trigger start of anaphase • Signals from outside the cell • Environmental conditions

22. Checkpoints

23. Checkpoints • G1- before S phase- most important in animal cells • If doesn’t pass checkpoint- arrested forever • Ex: nerve and muscle cells • G2- before M phase • M checkpoint- if chromosomes are all attached to spindles chromatids separate

24. How are signals to continue cycle relayed? • Signal transduction- growth factors relay signals to continue cycle

25. Does it ever go “out of control”? • Cancerous cells- dysfunctional cell cycle control, divides uncontrollably and can invade body tissues • Tumor- abnormal mass of cells • Benign tumor- excess mass of normal cells, remain in same place of body • Malignant tumor- cancerous, mass of cancerous cells capable of spreading into neighboring tissues • Displaces normal tissue as it grows • Metastasis- spread of cancerous cells beyond original site • 4 categories depending on where they originated • Unrestrained by cell cycle control, not affected by density, don’t need to be anchored, can synthesize growth factor • Chemotherapy and radiation- attempt to stop cell division

27. Meiosis • gamete production, occurs in ovaries and testes, produces cells with ½ chromosome number, haploid cells

28. Vocabulary • Somatic cell- body cell • Homologous chromosomes- same chromosome, same genes, consists of sister chromatids • Autosomes- chromosomes not involved in sex determination • Sex chromosomes- X and Y, determines sex

30. Vocabulary con’t • Diploid cells- contain 2 homologous sets of chromosomes, 2n, body cells for ex • 2n in humans = 46 • Haploid cells- contain 1 set of chromosomes, gametes, sex cells, n • n in humans = 23 • Fertilization- joining of haploid sperm and egg cells • Zygote- fertilized egg

31. Meiosis • Produces 4 haploid cells • Undergoes 2 divisions: meiosis I and meiosis II • Meiosis I- homologous chromosomes separate • Meiosis II- no duplication, only division • Interphase- same as in mitosis

32. Steps in meiosis • Prophase 1- similar to mitosis, synapsis- homologous chromosomes come together in pairs, forming a tetrad (4 chromatids) – crossing over occurs- segments of chromosomes are exchanged • Metaphase 1- tetrads line up along metaphase plate • Anaphase 1- tetrads are pulled to opposite ends • Telophase and cytokinesis- same as mitosis and is followed by another interphase before meiosis II • Meiosis II- NO DUPLICATION, similar steps as meiosis I and mitosis • Results in 4 daughter cells each with ½ the number of chromosomes as parent cell

35. Mitosis vs. Meiosis

36. Sexual reproduction= variation • Independent assortment- how chromosomes are arranged at metaphase plate meiosis I and II

37. More ways that affect variation: • Crossing over- exchange of homologous chromosomes segments • Chiasma- site of crossing over • Results in genetic recombination, produces new gene combinations

38. More ways that affect variation: • Chromosomes carry different versions of genes • Alleles- different versions of a gene

39. Do mistakes happen in meiosis? • Nondisjunction- chromosomes do not separate

40. Nondisjuction • In autosomes- can be lethal, or can affect survival • Trisomy 21 (Down syndrome) • Trisomy 13 (Patau syndrome), Trisomy 18 (Edwards syndrome) • In sex chromosomes- abnormalities do not affect survival • Klinefelter syndrome- extra X’s – (male) • XYY- normal male • XXX-metafemale • Turner syndrome- XO- female- absence of Y chromosome • All affect fertility of afflicted individual, except XYY

41. Do mistakes happen in meiosis? • Chromosomal abnormalities • Deletion- fragment of chromosome is deleted/lost • Duplication- part of chromosome is added to the homologous chromosome • Translocation- chromosome fragment is attached to another chromosome • Inversion- fragment is chromosome is attached in reverse direction

42. How can we see the mistake? • Karyotype- magnified image of chromosomes • Errors in meiosis can lead to gametes with abnormal chromosome numbers • Fertilization of gametes with abnormal chromosomes numbers can lead to offspring with chromosomal abnormalities • Ex: Down syndrome- trisomy 21

43. Do humans help out what traits get passed down? • Selective breeding- breeding certain individuals with desired traits • Crops • Racehorses • Farm animals • Dogs