1. Cell Cycle and Mitosis

2. Cell Cycle and Mitosis
Cell Division — process by which a cell divides into 2 new cells
2 Daughter Cells
Parent Cell
The original cell is called the parent cell; 2 new cells are called daughter cells
2 Daughter Cells
Parent Cell

3. Why do cells need to divide?
Living things grow by producing more cells, NOT because each cell increases in size
Repair of damaged tissue
If cell gets too big, it cannot get enough nutrients into the cell and wastes out of the cell

4. Do you remember? DNA Nucleus Genetic Information
1) Which cell organelle controls all cell functions? 2) What does this cell organelle contain? 3) What do ALL cells need in order to have the directions/code to perform functions correctly?
Nucleus
Genetic Information
DNA

5. DNA
DNA is located in the nucleus and controls all cell activities including cell division
Long and thread-like DNA in a non-dividing cell is called chromatin
Doubled, coiled, short DNA in a dividing cell is called chromosome
Consists of 2 parts: chromatid and centromere

6. Compare and Illustrate DNA
DNA in NON-DIVIDING Cell
DNA in a DIVIDING Cell

7. Coils up into chromosomes
Chromatin to chromosomes illustration:
Chromatin
Coils up into chromosomes
Duplicates itself
Why does DNA need to change from chromatin to chromosome?
More efficient division

8. 2 identical “sister” chromatids attached at an area in the middle called a centromere
When cells divide, “sister” chromatids separate and 1 goes to each new cell

9. Cell Cycle and Mitosis
Before cell division occurs , the cell replicates (copies) all of its DNA, so each daughter cell gets complete set of genetic information from parent cell
Each daughter cell is exactly like the parent cell – same kind and number of chromosomes as the original cell
Every organism has its own specific number of chromosomes
Examples: Human = 46 chromosomes or 23 pairs
Dog = 78 chromosomes or 39 pairs
Goldfish = 94 chromosomes or 47 pairs
Lettuce = 18 chromosomes or 9 pairs

10. All somatic (body) cells in an organism have the same kind and number of chromosomes.
Examples: Human = 46 chromosomes
Human skin cell = 46 chromosomes
Human heart cell = 46 chromosomes
Human muscle cell = 46 chromosomes
Fruit fly = 8 chromosomes
Fruit fly skin cell = 8 chromosomes
Fruit fly heart cell = 8 chromosomes
Fruit fly muscle cell = 8 chromosomes

11. Cell Cycle -- series of events cells go through as they grow and divide
Cell grows, prepares for division, then divides to form 2 daughter cells – each of which then begins the cycle again

12. Cell Cycle Outline Interphase Mitosis Cytokinesis G1: Cell Grows
S: DNA Replicates
G2: Growth & prepares for division
Mitosis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

13. Cell Cycle and Mitosis Interphase Prophase Metaphase Anaphase
Get a friend and create a sentence to help you remember the order of the cell cycle and mitosis. Use the first letter of each term.
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

14. Interphase Interesting things happen! Cell preparing to divide
Genetic material doubles
Cells most of their time in Interphase 14

15. Mitosis Begins Prophase, Metaphase, Anaphase, Telephase
Mitosis – division of the nucleus into 2 nuclei, each with the same number of chromosomes
Mitosis occurs in all the somatic (body) cells
Mitosis Begins Prophase, Metaphase, Anaphase, Telephase

16. Prophase Chromosome pair up! Chromosomes become visible Prophase
Nuclear membrane disappears
Spindle fibers form
Prophase 16

17. Metaphase Chromosomes meet in the middle!
Spindle Fibers connect to chromosomes
Metaphase 17

18. Anaphase Chromosomes get pulled apart
Spindle fibers pull chromosomes to opposite sides 18

19. Telophase Now there are two! Chromosomes uncoil
Spindle fibers disappear
Two nuclei are formed
Telophase 19

20. Cytokinesis
Cytokinesis — the division of the rest of the cell (cytoplasm and organelles) after the nucleus divides
In animal cells the cytoplasm
pinches in
In plant cells a cell plate forms
After mitosis and cytokinesis, the cell returns to Interphase to continue to grow and perform regular cell activities

21. Mitosis is a type of asexual reproduction.
There are two types of reproduction:
Asexual Reproduction
Sexual Reproduction
parent reproduces by itself
offspring is genetically identical to “mamma”
Offspring is genetically unique
creates diversity within population

22. Asexual Reproduction Mitosis Binary Fission Budding Spores
Regeneration
Vegetative Propagation

23. 1) Mitosis 2) Binary Fission
a parent cell splits into 2 daughter cells of = size
w/ prokaryotes
produce 2 identical daughter cells with the same # of chromosomes as the parent cell. (identical)

24. 3) Budding
4) Spores
spores are surrounded by a tough coat to help them survive harsh conditions. .. Produced and released
a new, duplicate organism forms at the side of the parent and enlarges until an individual is created.

25. 6) Vegetative Propagation
5) Regeneration
6) Vegetative Propagation
stolons
growth of new tissues/organs to replace those injured or lost.
Common in invertebrates, especially Asteroidea (Sea Stars) and Annelida (Worms).
* In some multicellular plants
* new plants develop from the roots, stems, or leaves of the parent.

26. Sexual Reproduction Meiosis
Cell division that results in haploid gametes; used for sexual reproduction

27. Haploid?
When a gamete (sperm or egg) of an organism has HALF of the full amount of chromosomes
Hap Half
Remember, human cells have 46 chromosomes? Then the haploid # is 23
Sperm
Egg

28. Meiosis Meiosis I Meiosis II
Occurs in the same four phases as mitosis but in two steps: Meiosis I and Meiosis II
Meiosis I
All chromosomes make copes of themselves
This doubles the # of chromosomes in the cell
Meiosis II
Begins in same two cells created by Meiosis I
Creates FOUR new haploid cells
Occurs in a manner very similar to mitosis

29. Outline of Meiosis Meiosis I Meiosis II Prophase I Metaphase I
Anaphase I
Telophase I
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II

30. Prophase I Homologous chromosomes from each parent pair up!
They form two attached sets of chromatids called a tetrad
There are MANY ways the chromatids can line up: this is one source of genetic variation.
Homologous chromosomes:
1 from each parent
carry genes that control the same
inherited traits. 30

31. Metaphase I Each tetrad meets in the middle!
Spindle fibers connect centromeres
Crossing over of chromosomes may occur to provide additional genetic variation – 2nd source of genetic variation 31

32. Anaphase I Homologous chromosomes move to opposite ends
Tetrads get pulled apart
Homologous chromosomes move to opposite ends 32

33. Telophase I
Cells may finish cytokinesis OR proceed immediately with Meiosis II 33

34. Prophase II Chromosomes did NOT replicate
At this point, the cell is haploid because it no longer has one of every kind of chromosome that was in the original cell 34

35. Metaphase II
Sister chromatids line up on individual spindle fibers 35

36. Anaphase II Sister chromatids are separated into each new cell
Each new cell now has only HALF as many chromosomes as the parent cell in Prophase I 36

37. Telophase II
Each of the four new cells completes reforming nuclei and cytokinesis separates the four new hapliod cells 37

38. How does meiosis lead to genetic variation?
Look back at Prophase I & Metaphase I, what may lead to genetic variation?
There are MANY ways the chromatids can line up
Crossing over of chromosomes may occur
What is another factor that could lead to genetic variation?
Random combinations of sperm and eggs

39. Review! Interphase Interphase Prophase 1 Metaphase 1 Meiosis 1
Anaphase 1
Telophase 1

40. Prophase 2
Metaphase 2
Meiosis 2
Anaphase 2
Cytokinesis
Cytokinesis

41. Note.. Male gametes Female gametes 4 haploid gametes …
4 sperm by way of spermatogenesis
Female gametes
4 haploid gametes …
1 Ovum (egg) & 3 Polar Bodies by way of oogenesis

42. Sometimes cell division doesn’t go as planned…

43. Cell Division Regulation
Internal and external factors regulate cell division.
Cancer is the uncontrolled growth and division of cells.
Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function.

44. Cancer Benign – cancer cells typically remain clustered together
Malignant – cancer cells can break away or metastasize
cancer cell
bloodstream
normal cell
metastasize
Benign
Malignant

45. Causes of Cancer Internal Factors External Factors Inheritance
Mutations
Skin Cancer
External Factors
Carcinogens are substances that are known to produce and promote the development of cancer.
Radiation
Chemical
Viruses

46. Nondisjunction Mutations
Improper separation of sister chromatids may result in a cell having one too many chromosomes (trisomy) or not having one of a certain chromosome (monosomy)
Karyotype – a picture of an individual’s chromosomes so that the types of mutations might be seen

47. Trisomy 21 – Down Syndrome
Trisomy 18 - Edward's Syndrome

48. Meiosis Square Dance