1. Cell Division Mitosis vs. Meiosis
BIO.B – Describe the events that occur during the cell cycle interphase, nuclear division (mitosis and meiosis) and cytokinesis.

2. Chromosome Structure
Chromosomes – a single piece of coiled DNA and proteins found
in eukaryotic cells and prokaryotic cells.
Each organism has a specific number of chromosomes.
How many chromosomes are in human somatic (body) cells? ______
How many chromosomes are in a prokaryotic cell? ______________

3. Chromosome Structure Continued…
Chromosomes contain genes that code for specific traits (eye color, hair color, etc…).
View this video entitled “What are genes?”

4. Chromosome Structure Continued…
All of an organism’s genetic material (DNA) is its genome.
Uncondensed (uncoiled) DNA plus proteins is called chromatin.
One half of a duplicated chromosome is a chromatid.
Sister chromatids are held together at the centromere.
chromatid
Condensed, duplicated chromosome
centromere
Check out this link on “Chromosome Basics.”

5. The Cell Cycle
The cell cycle is a series of events that take place in EUKARYOTIC cells for the purpose of growth, tissue repair and reproduction.
There are three main events that occur during the cell cycle. These events include:
1. Interphase – preparation for cell division
2. Nuclear Division – division of the nucleus
3. Cytokinesis – division of the cytoplasm

6. The Cell Cycle Interphase consists of 3 phases:
What happens during the cell cycle?
Interphase – the longest part of the cell cycle in
which a cell performs the majority of its functions,
such as preparing for nuclear division and cytokinesis.
Interphase consists of 3 phases:
Gap 1 (G1) - Cell growth, normal functions, organelles duplicate
Synthesis (S) - DNA replication (Synthesis of DNA)
Gap 2 (G2) - Additional growth
2. Nuclear division – division of the nucleus
There are two types of nuclear division:
Mitosis – a nuclear division that results in 2 somatic (body) cells with identical DNA.
Meiosis – a two-phase nuclear division that results in the production of 4 gametes (sex cells) that are genetically different.
3. Cytokinesis - division of the cytoplasm

7. Nuclear Division: Mitosis vs. Meiosis

8. The Cell Cycle
Checkpoints in the cell cycle will only allow the cell to divide if the cell is large enough and the DNA is undamaged!
The surface area of a cell must be large enough for the transport of materials into and out of the cell.
Cells that are large tend to have different shapes to help them function properly.
The rate of cell division varies depending upon the location and function/type of the cell.
Some cells are unlikely to divide, such as neurons (nerve cells). These cells stay in a phase known as (G0).

9. MAJOR CHECKPOINTS G1 checkpoint G2 checkpoint M (Metaphase) checkpoint
Controlled by cell size, growth factors, environment
“Go”  completes whole cell cycle
“Stop”  cell enters non-dividing state (G0 Phase)
Nerve, muscle cells stay at G0; liver cells called back from G0
G2 checkpoint
Controlled by DNA replication completion, DNA mutations, cell size
M (Metaphase) checkpoint
Check spindle fiber (microtubule) attachment to chromosomes at kinetochores (anchor sites)

10. Cell Cycle Internal Regulatory Molecules
Kinases (cyclin-dependent kinase, Cdk): protein enzyme controls cell cycle; active when connected to cyclin
Cyclins: proteins which attach to kinases to activate them; levels fluctuate in the cell cycle

11. Internal Regulatory Molecules
MPF = maturation-promoting factor
specific cyclin-Cdk complex which allows cells to pass G2 and go to M phase

12. External Regulatory Factors

13. External Regulatory Factors
Growth Factor: proteins released by other cells to stimulate cell division
Density-Dependent Inhibition: crowded cells normally stop dividing; cell-surface protein binds to adjoining cell to inhibit growth
Anchorage Dependence: cells must be attached to another cell or ECM to divide

14. Uncontrolled Cell Division
Uncontrolled cell division results in tumors. Tumors can be malignant OR benign. Malignant tumors are cancerous and can metastasize within an organism.
Cancer cells do NOT carry out necessary functions.
Cancer cells come from normal cells with damage to the genes that are involved in cell cycle regulation.
Carcinogens are substances that cause these gene mutations.

15. loses anchorage dependency and density-dependency regulation
Normal Cells
Cancer Cells
Cancer: disorder in which cells lose the ability to control growth by not responding to regulation.
multistep process of about 5-7 genetic changes (for a human) for a cell to transform
loses anchorage dependency and density-dependency regulation

16. Mitosis Mitosis = Division of nucleus  Forms 2 somatic cells
Somatic cells = all body cells except sex cells/gametes
What are some examples of somatic cells that undergo mitosis?
Are somatic cells genetically identical? Do they have the same DNA?

17. Interphase -Preparing a cell for division
Parent cell
centrioles
spindle fibers
centrosome
nucleus with
chromatin (contains DNA)
Interphase prepares the cell to divide by growing and duplicating the DNA.
Chromatin and a nuclear membrane are both visible.

18. Prophase – 1st stage of mitosis
During prophase, chromatin condenses to form chromosomes and spindle fibers form.
The nuclear membrane begins to dissolve.

19. Metaphase – 2nd stage of mitosis
During metaphase, chromosomes line up in the middle of the cell attached to spindle fibers.

20. Anaphase – 3rd phase of mitosis
During anaphase, sister chromatids separate and travel to opposite sides of the cell.

21. Telophase – 4th & final stage of mitosis
During telophase, two new nuclei form and chromosomes begin to uncoil.

22. Cytokinesis – division of the cytoplasm
Cytokinesis differs in plant and animal cells.
In animal cells, the plasma membrane pinches closed.
In plant cells, a cell plate forms.

23. Which phases of the cell cycle can you identify?

24. Cell Differentiation
Although all somatic cells contain the same DNA they may perform different functions in an organism. This is due to a process called cell differentiation, in which a cell will develop into its mature form based on the DNA (genes) that is expressed (read).
Cells that perform similar functions are called tissues.
Tissues that work together to perform specific functions are called organs.
Organs that work together to perform specific functions form an organ system.

25. Stem Cells Stem cells are special cells that have the ability to:
divide and renew themselves
remain undifferentiated in form
develop into a variety of specialized cell types
Stem cell research has the potential to change medicine. Why?

26. Asexual Reproduction
Asexual reproduction is the creation of offspring from a single parent. It forms offspring identical to the parent.
Environment determines what form of reproduction is most advantageous. For example:
Asexual reproduction is an advantage because organisms d0 not need to waste time and energy looking for a mate. Asexual reproduction occurs more quickly than sexual reproduction.
A disadvantage to asexual reproduction is that genetically identical organisms are produced; therefore during unfavorable conditions an entire population can be harmed.

27. Asexual Reproduction in Prokaryotes
All prokaryotes reproduce asexually by a process known as binary fission.
Binary fission is the splitting of a parent cell into two genetically identical daughter cells.
How is similar to mitosis? How is it different? (Look at the diagram.)

28. Asexual Reproduction in Eukaryotes
Some eukaryotes can reproduce asexually by mitosis. There are different types of mitotic reproduction which include:
Budding (Yeast – diagram 1)
Fragmentation/Regeneration (Planaria – diagram 2)
Vegetative Propagation (Strawberries – diagram 3)

29. Budding
Budding - forms a new organism from a small projection growing on the surface of the parent.
bud
Hydra
Yeast

30. Fragmentation OR Regeneration
Fragmentation or (regeneration) is the splitting of the parent into pieces that each grow into a new organism.
Can you think of any
organisms that regenerate?

31. Vegetative Propagation
Vegetative reproduction forms a new plant from the modification of a stem or underground structure on the parent plant.
Do you know of any plants
that use vegetative
propagation to reproduce?

32. Sexual Reproduction
During sexual reproduction offspring are formed from two parents. Both parents produce sex cells called gametes.
Male Gamete vs. Female Gamete
SPERM EGG
Fertilization must occur for sexual reproduction to be successful. Fertilization is the joining of a sperm and an egg.

33. Types of Cells
Body cells are also called somatic cells. They are formed by MITOSIS.
Somatic cells are located throughout the body (heart, brain, stomach, lung, skin, etc…)
DNA in your somatic cells is NOT passed on to your children.
Germ cells develop into gametes. They are formed by MEIOSIS.
Germ cells are located in the ovaries and testes.
DNA in your gametes IS passed on to your children.

34. Haploid vs. Diploid Cells
Somatic cells (body cells) are diploid cells. Diploid cells (2n) have two copies of every chromosome. One copy comes from your mother and one copy comes from your father.
Gametes (sperm and eggs) are haploid cells. Haploid cells (n) have one copy of each chromosome.
What is the human haploid number? (n = 23) Diploid number? (2n = 46)
Mitosis makes diploid cells Meiosis makes haploid cells.

35. Types of Chromosomes All cells contain DNA located in chromosomes.
Cells have two types of chromosomes:
Autosomes: Non-sex chromosomes (Pairs 1-22)
Sex Chromosomes: Chromosomes that contain genes related to your sex. (Pair 23)
XX = female
XY = male
Karotype – picture of all the chromosomes in a diploid cell.

36. Homologous Chromosomes
Homologous chromosomes: Chromosomes that have the same structure and contain the same genes in the same locations.
In a homologous pair of chromosomes, one chromosome is inherited from mom and one chromosome is inherited from dad.
View this video entitled “Where do your genes come from?”

37. Meiosis
Meiosis = A type of nuclear division that divides a diploid cell into four haploid cells.
Meiosis is the process that forms gametes (sperm and eggs); therefore it is necessary for sexual reproduction to occur.

38. Meiosis
Germ cells (46 chromosomes) undergo two rounds of cell division, which results in cells with a reduced number of chromosomes (23 chromosomes).
Interphase occurs before Meiosis I (the first division) but DOES NOT occur before Meiosis II (the second division).
Meiosis increases genetic variation and diversity.

39. Stages of Meiosis I
What is a tetrad? Homologous chromosomes line up together to form tetrads in a process called synapsis.

40. Check out these meiosis videos:
Stages of Meiosis II
Check out these meiosis videos:
Video #1
Video #2

41. Name That Phase!

42. Crossing Over
Crossing over: An exchange of genetic material between homologous chromosomes during prophase I of meiosis.
Crossing over increases genetic variability (differences) in gametes.

43. Quiz yourself at neok12.com/Cell-Division.htm
Mitosis Vs. Meiosis
Mitosis has one cell division.
Meiosis has two cell divisions.
During meiosis homologous
chromosomes pair up. During
mitosis homologous chromosomes
never pair up.
Quiz yourself at neok12.com/Cell-Division.htm

44. Gametogenesis
Where does MEIOSIS occur???? Meiosis occurs in organs called gonads.
Female gonads are ovaries.
Male gonads are testes.
Inside the gonads are germ cells. Germ cells produce gametes by the process of meiosis.
Female germ cells = oocytes
Male germ cells = spermatocytes
Oocytes are formed by a type of meiosis called oogenesis. Spermatocytes are formed by a type of meiosis called spermatogenesis.

45. Oogenesis Vs. Spermatogenesis

46. Reproductive Organs
MALE
FEMALE

47. Fertilization and Beyond…..
1st: Fertilization – joining of sperm and egg
2nd: Growth and Development – occurs by the process of MITOSIS
Zygote Embryo  Fetus  Infant

48. Embryo  Fetus  Infant

49. Pregnancy & Birth

50. Advantages to Sexual Reproduction
Greater variety/diversity in organisms.
Greater ability to adapt and evolve.
Disadvantages:
Requires more energy than asexual reproduction.
Requires more time (finding a mate) than asexual reproduction.