1. Chapter 8: Cell Reproduction
Essential Question: How do organisms grow? How do cells reproduce by cell division?

2. Chromosomes: rod-shaped structures made of DNA and proteins
A. Chromosome structure
1. Each chromosome is a single DNA molecule associated with proteins that is tightly coiled
2. Chromosomes are visible during cell division under a microscope
3. Histones: proteins that help maintain the shape of chromosomes

4. a) DNA wraps around the proteins
b) Helps to package DNA tightly
4. Nonhistone: proteins that do not participate in the packing of DNA but control the activity of specific regions of the DNA
5. Chromatid: one of the two identical
parts of the chromosome
a) chromatids form as the DNA makes a copy of itself before cell division
b) when the cell divides, each of the two new cells will receive one chromatid from each chromosome

5. 6. Centromere: holds the two chromatids together until they separate during cell division
7. When the cell is not dividing the DNA is not so tightly coiled and is called chromatin
Chromosome
B. Chromosome numbers: each species has a characteristic number of chromosomes in each cell

7. Sex chromosomes: chromosomes that determine the sex of an organism and may carry genes for other characteristics
a) Humans: sex chromosomes are X and Y
b) females have two X chromosomes
c) males have X and Y

8. 2. Autosomes: chromosomes that are not sex chromosomes
a) humans have 44 autosomes
b) humans have 2 sex chromosomes
3. Every cell produced by sexual reproduction has two copies of each autosome (one from each parent)

9. 4. Homologous chromosomes: two copies of each autosome
a) same size and shape
b) carry genes for the same traits (eye color)
5. Karyotype: photomicrograph of the chromosomes found in a normal human and shows the 46 human chromosomes exist as 22 homologous pairs of autosomes and two sex chromosomes

12. Genetic Disorders

13. C. Diploid and Haploid cells
1. Diploid: cells having two sets of chromosomes
a) Have both chromosomes for each homologous pair
b) Have 2 sex chromosomes
c) All normal human cells except reproductive cells (sperm and egg cells) are diploid
d) Abbreviates as 2n
e) 2n number in humans is 46 (22 pairs of homologous chromosomes and 2 sex chromosomes)

14. 2. Haploid: cells that contain only one set of chromosomes
a) sperm cells and egg cells
b) Have half the number of chromosomes that are present in diploid cells
c) Have only one chromosome of each homologous pair and only one sex chromosome
d) Abbreviated as 1n
Diploid and haploid

15. 3. When a sperm cell (1n) and egg cell (1n) combine to create the first cell of a new organism the new cell will be diploid (2n)

16. II. Cell Division: process by which cells produce offspring cells
A. Cell division in Prokaryotes
1. Binary fission: division of prokaryotic cell into two offspring cells
2. Three general stages
a) Chromosome makes a copy of itself and attaches to the inside of the cell membrane
b) Cell grows until it is twice the original size
c) Cell wall forms between the two chromosomes and the cell splits into two new cells

18. B. Cell Division in Eukaryotes
1. Two types
a) Mitosis: new cells with genetic material that is identical to that of the original cell
b) Meiosis: reduces the chromosome number by half in the new cells
2. Cell cycle: repeating set of events that make up the life of a cell include interphase and cell division

19. Concept Map Cell Cycle includes M phase (Mitosis) Interphase
is divided into
is divided into
G1 phase
S phase
Prophase
G2 phase
Metaphase
Telophase
Anaphase

20. The Cell Cycle
Section 10-2
G1 phase
M phase
S phase
G2 phase

21. 3. Interphase: time between cell division
a) G1 phase (gap): cell growth
b) S phase (synthesis): DNA is copied
c) G2 phase: preparation for cell division
4. Cell can exit the cell cycle and enter G0 phase, stop dividing (nervous system cells)
Cell cycle

22. C. Control of Cell Division
1. Proteins regulate the progress of cell division at certain checkpoints (traffic signals)
a) green light: go to next stage
b) red light: halt or stop
2. Three checkpoints

23. a) Cell growth (G1) checkpoint: if cell is healthy and large enough it will go to S phase
DNA synthesis (G2) checkpoint: DNA repair enzymes check the results of DNA replication and if everything is correct, it can move to the next step
Mitosis checkpoint: signals the cell to exit mitosis and enter G1 phase

24. When control is lost: Cancer
a) Proteins that control cell growth and division are coded for by genes
b) If a mutation occurs in the genes, the proteins may not work properly
c) Cell growth and division may not work correctly
d) Cancer: uncontrolled growth of cells
Cell cycle and cancer

25. D. Mitosis: division of the nucleus and is divided into four phases
1. Prophase
a) DNA becomes visible as tight coils
b) Nuclear membrane breaks down
c) Centrosomes appear and move to opposite poles of the cell: two dark spots containing centrioles

26. d) Spindle fibers: microtubules that come out of the centrosomes
e) Mitotic spindle: made of spindle fibers and is used to equally divide the chromatids between the two cells

27. Prophase Interphase Prophase Cytokinesis Metaphase Telophase Anaphase
Spindle forming
Centrioles
Nuclear envelope
Chromatin
Centromere
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

28. 2. Metaphase
a) spindle fibers move the
chromosomes to the center of the dividing cell
b) held in place at the center of the cell
3. Anaphase
a) chromatids of each chromosome separate at the centromere
b) move towards opposite poles of
the cell

29. Metaphase Interphase Prophase Cytokinesis Metaphase Telophase Anaphase
Spindle forming
Centrioles
Nuclear envelope
Chromatin
Centromere
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

30. Anaphase Interphase Prophase Cytokinesis Metaphase Telophase Anaphase
Spindle forming
Centrioles
Nuclear envelope
Chromatin
Centromere
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

31. 4. Telophase
a) spindle fibers break apart
b) chromosomes begin to uncoil and become invisible
c) nuclear envelope forms

32. Telophase Interphase Prophase Cytokinesis Metaphase Telophase Anaphase
Spindle forming
Centrioles
Nuclear envelope
Chromatin
Centromere
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

34. E. Cytokinesis: cytoplasm of the cell divides
1. Animal cells: cell membrane pinches inward between the dividing cell’s two poles
a) cleavage furrow: area of the cell membrane that pinches in
b) cell is split into two cells

35. 2. Plant cells: cell plate: membrane-bound cell wall that forms in between the dividing cell and forms two cells
Mitosis Video Clip

36. Cytokinesis Interphase Prophase Cytokinesis Metaphase Telophase
Spindle forming
Centrioles
Nuclear envelope
Chromatin
Centromere
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

37. 1. Gametes: haploid reproductive cells
III. Meiosis
A. Meiosis: process of nuclear division that reduces the number of chromosomes in new cells to half the number in the original cell
1. Gametes: haploid reproductive cells
a) sperm cells and egg cells that are (1n)
b) contain 23 chromosomes
2. Sperm and egg cell together form a zygote that contains 46 chromosomes (2n)

38. B. Stages of Meiosis
1. Cells undergoes G1, S, and G2 phases so there is a duplicate set of chromosomes, so cells need to divide twice
2. First division is called meiosis I and creates 2n cells
3. Second division is called meiosis II and creates 1n cells

39. C. Meiosis I
1. Prophase I: DNA tightly coiled and spindle fibers appear
a) synapsis: every chromosome lines up next to its homologue
b) tetrad: each pair of homologous chromosomes
c) crossing over: chromatids twist around one another and sometimes a portion may break off and attach to adjacent chromatids ( permits exchange of genetic material)Crossing over

41. d) genetic recombination: new mixture of genetic material
2. Metaphase I: tetrads line up randomly along the midline of the cell
a) spindle fibers from one pole attach to the centromere of one of the homologous chromosomes
b) spindle fibers from the other pole attach to the centromere of the other homologous chromosome

42. 3. Anaphase I: each homologous chromosome (2 chromatids attached by a centromere) moves to an opposite pole
a) independent assortment: random separation of the homologous chromosomes
4. Telophase I: chromosomes reach the opposite ends of the cell and cytokinesis begins
a) two new cells are formed
b) each cell has 46 chromosomes

43. 5. During meiosis I: two new cells produced each containing one chromosome from each homologous pair
a) Each new cell contain two copies of the chromosome because the original cell copied its DNA before meiosis I

44. Meiosis I Interphase I Section 11-4 Prophase I Metaphase I Anaphase I
Cells undergo a round of DNA replication, forming duplicate Chromosomes.
Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.
Spindle fibers attach to the chromosomes.
The fibers pull the homologous chromosomes toward the opposite ends of the cell.
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45. D. Meiosis II: occurs in each cell formed during meiosis I and the DNA is not copied
1. Prophase II: spindle fibers form and move the chromosomes toward the middle
2. Metaphase II: chromosomes move to the middle and face opposite poles
3. Anaphase II: chromatids separate and move toward opposite poles
4. Telophase II: nuclear membrane forms

46. Meiosis II Meiosis II Prophase II Metaphase II Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

47. 5. Cytokinesis II: creates 4 new cells each containing half of the original cell’s number of chromosomes
Meiosis Comparing mitosis and meios

48. E. Formation of Gametes 1. Meiosis produces haploid reproductive cells (gametes) 2. Meiosis only occurs in reproductive organs (testes and ovaries)

49. 3. Male gametes: sperm cells or spermatozoa
a) spermatids: diploid reproductive cell divides by meiosis to form four haploid cells
b) spermatogenesis: production of sperm when spermatids develops into a mature sperm cell
4. Female gametes: egg cells or ova
a) ovum: diploid reproductive cell divides by meiosis to form one egg cell (uneven dividing of the cell during cytokinesis I and II)

50. b) polar bodies: three other products that degenerate
c) oogenesis: production of mature egg cells
Gamete

52. F. Asexual and Sexual Reproduction
1. Asexual reproduction: production of offspring from one parent
a) does not involve meiosis or union of gametes
b) unicellular organisms: binary fission or mitosis
c) multicellular organisms: budding off of portions of their bodies
d) offspring are genetically identical to parents

53. 2. Sexual reproduction: production of offspring through meiosis and the union of a sperm and egg
a) offspring are genetically different from the parents because genes are combined in new ways in meiosis
b) offspring contain a unique combinations of their parents genes
c) sexual reproduction enables species to adapt to new conditions Reproduction

54. Concept Map
Words to use Cell Division Meiosis 2 identical cells Mitosis 4 gamete cells Prophase Metaphase Anaphase Telophase Meiosis I 4 phases Meiosis II 1 division 2 divisions Half # of chromosomes Same # of chromosomes