1. Cell Reproduction
Chapter 9

2. Cell Growth
Main Idea: Cells grow until they reach their size limit, then stop growing or divide
Objectives:
Explain why cells are relatively small
Summarize the primary stages of cell cycle
Describe the stages of interphase
Review: What’s the cell theory say?
All organism are made of cells
Cells are the smallest unit of living organisms
Cells only come from other cells

3. Cell Size Imagine yourself on a tennis court playing 1 on 1.
Wouldn’t it be hard if the court were the size of a football field?
Cells have a size limit to ensure all the needs of the cell are met

4. Surface Area to Volume
Limits to cell size: ratio of its surface area to its volume
Surface area is the area covered by the plasma membrane
Volume is the space inside the cell
Figure 9.1 and Pg. 244 Connection to Math
By remaining small, cells have a much higher ratio of surface area to volume and can sustain themselves easier
Demo!
So: Do large cells perform their tasks more efficiently than small cell?
Mini Lab pg. 245

5. More About Size…
Small cells can transport substance easier than large cells
Diffusion would not be efficient, since it is passive transport, if the cell were large
It would be like trying to float a toy boat across a small puddle or across a large pond
Cell size also limits the ability of a cell to communicate
Signals for processes might not occur fast enough to signal another reaction
Signals for protein synthesis need to reach the ribosomes in time to continue the cycle

6. What happens when a cell reaches its size limit?
It will either:
Stop growing
Divide
Most cells divide because it prevents the cell from becoming too large and it helps the cell reproduce
Cell Cycle: the growing and dividing of cells
There are 3 main stages
Interphase, Mitosis, Cytokinesis
Time of division varies with the cell
Most cells take hours to divide in animals

7. Cell Cycle
During Interphase, the cell grows, develops, duplicates its DNA and prepares for division
Three stages of Interphase: G1, S and G2

8. Cell Cycle Interphase: Cells spend most of their life
G1 stage- Time immediately after the cell divides; cells grow to mature size
G stands for “Gap” time between cell reproductions
Some cells don’t divide after this
Example: nervous system cells only divide once
S Phase- DNA is copied
G2 stage- Cell prepares for division

9. Find your 7 o’clock partner
Designate partner A and partner B
Partner A asks: What are the stages of the cell cycle?
Partner B: What occurs in G1?
PA: What happens in G2?
PB: What’s the S phase?

10. Review
Main Idea: Cells grow until they reach their size limit, then stop growing or divide
Objectives:
Explain why cells are relatively small
Summarize the primary stages of cell cycle
Describe the stages of interphase

11. Section 9.2
Main Idea: Eukaryotic cells reproduce by mitosis, the process of nuclear division and cytokinesis, the process of cytoplasm division.
Objective: Describe the events of each stage of mitosis
Objective: Explain the process of cytokinesis

12. Think of events in your life that are cyclical
Example: The passing of comets in the year
Deer in the rut
Turkeys in spring breeding season
Day routine

13. Mitosis
Goal: replicated genetic material separates and the cell prepares to split into two cells
Why?
It allows genetic information to be passed onto daughter cells
Uses?
Replace damaged cells
Increases the cell number of an organism- in other words, the organism grows
SQR3 for “The Stages of Mitosis”, pg. 248

14. Chromosomes Contain coiled DNA and proteins
Chromatin is the relaxed form of DNA in the cell’s nucleus, looks like a single strand
Sister chromatids are structures that contain identical copies of DNA
Centromere holds the sister chromatids together
Socks!!

17. Mitosis Prophase: Longest phase Chromatin tightens into chromosomes
The chromosomes become shaped like an X
Centromeres are present
Nucleus disappears
Microtubules called spindle fibers form in the cytoplasm
Centrioles (also microtubules) migrate to the end of the cell (only in animal cells)
Spindle apparatus: name given to the group of spindle fibers, centrioles, etc. that help move the chromosomes around in the cell

18. Mitosis Prophase Cont’d: Nuclear envelop disappears
Spindle fibers attach to the sister chromatids to move the chromosomes around

19. Mitosis Metaphase Chromosomes are easy to identify Spindle fibers move
chromosomes to center
of cell

20. Anaphase
Chromatids are separated and move toward opposite poles caused by shortening spindle fibers
Whiles the chromatids separate, they are considered to be individual chromosomes
Centromere first

21. Telophase Spindle fibers disappear after chromosomes are separated
Chromosomes loosen up
Nuclear envelope and nucleus reappears

22. Mitosis
Cytokinesis:
Cell pinches inward and cytoplasm seperates cell into two new cells
Cleavage furrow appears and cell divides (animals)
Cell Plate (plants)

23. Animations Mitosis Video Fly Mitosis Cells Alive Mitosis
Interactive Classroom Video

24. Onion Root Tips

25. Review
Main Idea: Eukaryotic cells reproduce by mitosis, the process of nuclear division and cytokinesis, the process of cytoplasm division.
Objective: Describe the events of each stage of mitosis
Objective: Explain the process of cytokinesis
Card Sort on Mitosis Stages
What are the two differences between plant and animal cells in mitosis?

26. Cell Cycle Regulation
The timing and rate of cell division are important
Cyclins (proteins) bind to an enzyme, cyclin-dependent kinases, to start the different stages of cell cycle

27. Cancer
Although cell cycle has a system of checks for quality, sometimes things go wrong
Cancer is the uncontrolled growth and division of cells (caused by the failure of the regulation of the cell cycle)
Cancer cells spend less time in interphase
Pg. 254 picture

28. What effect do you think the difference in times have on the organism?
Stomach Cells
Normal Chicken
Interphase 120 min
Prophase 60 min
Metaphase 10 min
Anaphase 3 min
Telophase 12 min
Cancerous Chicken
Interphase 16 min
Prophase 15 min
Metaphase 2 min
Anaphase 1 min
Telophase 3 min
What effect do you think the difference in times have on the organism?

29. Causes of Cancer Does not just occur in weak organisms
Mutations or changes in the DNA, usually that control the cell cycle, cause cancer
Often, the mutations are repaired
Environmental factors
Smoking, asbestos, chemicals, etc
Radiation, x-rays
Not all cancers can be prevented
Genetics

30. Apoptosis Programmed cell death Why would cells WANT to die?
Cells in hands and feet
Tree leaves falling in autumn
Cells that are damaged

31. Stem Cells Discovered in 1998 Unspecialized cells Embryonic Adult
Results after a sperm fertilizes an egg
controversial
Adult
Found in tissues in body
Can be used to maintain/repair the same kind of tissue they came from
Newborns have adult stem cells
Less controversial

32. Paralysis Cured? Pg. 258 Mapping Stem Cells MJF Video
Video- Terra Incognita

33. Meiosis- Sect. 10.1 Main Idea: Meiosis produces haploid gametes
Objectives: Explain the reduction in chromosome number that occurs during meiosis
Recognize and summarize the stages of meiosis
Analyze the importance of meiosis in providing genetic variation

34. Which Cells?
The only cells that go through meiosis are the reproductive cells
The results of meiosis are sperm or egg cells
In females: meiosis takes place in the ovaries, before birth
In males: meiosis takes place in the testes, usually starting at puberty

35. Chromosomes Instructions for traits are located on chromosomes
Found in the nucleus
DNA on chromosomes is arranged as genes (which control the production of proteins)
Chromosomes consist of hundreds of genes

36. Homologous Chromosomes
Human body cells have 46 chromosomes
At conception, each parent contributes 23 chromosomes
The chromosomes that match from each parent make homologous chromosomes
They have the same length, same genes and same centromere position

37. Haploid and Diploid
Gametes: sex cells that have half the number of chromosomes
Gamete number change with the species
n represents the haploid chromosome number
Fertilization is the process when one haploid gamete combines with another
n + n = 2n
2n represents the diploid number

38. Numbers
Different species have different number of chromosomes

39. Meiosis Remember: Gametes are formed during meiosis
It reduces the number of chromosomes in the cell
When the gametes combine (sperm and egg) a zygote is formed (a diploid group of cells that grow into an embryo)
Meiosis consists of two stages

40. Meiosis I Meiosis I: MOST of the phases are the same as mitosis:
Interphase, prophase, metaphase, anaphase and telophase
Exception:
Prophase I-Instead of pairing on top of each other, they pair side by side with the homologue – Synapsis is the name given to the pair

41. Meiosis I
Crossing-over occurs in Prophase I: genes are shared from each pair
Norwegian wrestling…
Results in genetic recombination

42. Meiosis I
Metaphase I: the pairs of homologous chromosomes line up at the equator of the cell
Can we borrow you shoes?

43. Meiosis I
Anaphase I- Instead of pulling apart the single chromosome, the homologous pairs are separated
Chromosome number is reduced from 2n to n when the pairs get separated

44. Meiosis I
Telophase I: new cells are haploid, but still has it’s sister chromatid
The chromatids might not be identical anymore
After cytokinesis, the cells go into interphase before the second set of divisions
But, the DNA is not duplicated

45. Meiosis II

49. Cytokinesis results in four haploid cells, each with n number of chromosomes.
Four cells are produced instead of two
Visualizing Meiosis
Meiosis Video
Comparison Video
United Streaming Video
Two interactive games online to quiz yourself with

50. Questions for you
1. How many chromosomes will there be in the gametes of an organism with 18 chromosomes?
What would happen if the sister chromatids of one pair did not separate during anaphase II?
Down Syndrome

51. Numbers
Karyotype:
Picture of the pairs
Of chromosomes in
a cell

53. Why is Meiosis Important?
It results in genetic variation
In Prophase I the homologous chromosomes line up randomly
Depending on the order they line up in determines who they “cross over” with

54. Asexual Reproduction Asexual- one parent
Does not involve meiosis or the union of gametes
Bacteria- prokaryotes
Offspring are identical to parents
Rely on binary fission or mitosis

55. Cell Division- Prokaryotes
Use binary fission
Three steps:
Chromosome copies itself
Cell grows double it’s size
New cell wall forms between the two chromosomes and the cell splits
Bet you wish Eukaryotes were that easy…

56. Sexual Reproduction
Offspring are genetically different from parents because genes are combined in meiosis
Twins, contain unique combinations of parents’ genes
Advantage, through evolution, offspring can adapt rapidly to new conditions
If disease strikes a crop of grain, the plants that survive have the genes to overcome the disease

57. Cell Division- Eukaryotes
Mitosis- results in new cells with genetic info identical to the old
Meiosis- reduces chromosome number by half, then join other cells to restore the diploid number

58. Review Sect. 10.1 Main Idea: Meiosis produces haploid gametes
Objectives: Explain the reduction in chromosome number that occurs during meiosis
Recognize and summarize the stages of meiosis
Analyze the importance of meiosis in providing genetic variation