1. Cell Reproduction
Mitosis vs. Meiosis

2. Mitosis Exit Ticket Questions
Copy these questions in your notebook and answer before the end of class. Show to Mrs. Millican before you leave. IT IS A GRADE!!!
What is the purpose of mitosis? What kind of cells does it occur in?
When is the DNA copied for the new cell?
How many chromosomes do human beings have?
Why aren’t chromosomes always visible?

3. How do little elephants grow up to be BIG elephants?

4. Why do animals shed their skin?

5. The process of asexual reproduction begins after a sperm fertilizes an egg.

6. Three reasons why cells reproduce by asexual reproduction/mitosis: 1
Three reasons why cells reproduce by asexual reproduction/mitosis: Growth Repair Replacement
Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun.
Cell that reproduce by asexual reproduction reproduce constantly.

7. Eukaryotic Cell Division
Two forms
Mitosis
grow, replace dead or worn out cells, or to repair wounds
Asexual reproduction in fungi, protists, some plants/animals
Meiosis
Sexual reproduction

8. Cell Division All cells arise from other cells by cell division.
When cells grow to a certain size they must either divide or die.
If a cell continued to grow without dividing, the surface area of the cell would become too small to hold the cell’s contents.

9. Cell Division
Cell division is a complex series of changes in the nucleus of a cell that leads to the production of two new cells.
The new cells are called daughter cells.
The nuclei of the daughter cells are usually identical to each other and to that of the parent cell.
The daughter cells grow and increase in size until they divide and produce two more daughter cells.
This process continues, resulting in organism growth and reproduction.

10. Mitosis
All cells in the body (except sex cells) are produced by the process of mitotic cell division.
Mitosis involves a complex series of changes in the nuclei of body cells that produce identical (same) daughter cells.
They have the same number and type of chromosomes as the parent cells.

11. The Cell Cycle – Stages of Mitosis
Although the events of mitosis are an ongoing process, they are generally described in terms of separate phases, or stages.
Interphase
Prophase
Metaphase
Anaphase
Telophase

12. Before Cell Division
Before mitosis can begin, the cells chromosomes must be duplicated. The familiar X shape usually shown in pictures of chromosomes is actually two chromosomes right before mitosis or meiosis.

13. A Karyotype is an Arranged Picture of Chromosomes At Their Most Condensed State
Note that almost all chromosomes come in homologous pairs.
A normal human karyotype

14. DNA is Condensed into Visible Chromosomes Only For Brief Periods in the Life of a Cell
95% of the time, chromosomes are like this.
Easily visible chromosomes are apparent perhaps 5% of the time in an actively growing cell and less in a non-growing cell.

15. DNA is Packaged into Chromosomes
chromatin
duplicated
chromosome
The packaging is impressive – 2 meters of human DNA fit into a sphere about meters in diameter.

17. Interphase Interphase is the period between cell divisions.
During interphase, the single-stranded chromosomes replicate (make an extra copy).
The chromosomes can not be seen during interphase.

18. Interphase Plant Cell Animal Cell
Photographs from:

19. Prophase
In prophase, the double-stranded chromosomes become visible, and the nuclear membrane disappears.
A spindle apparatus, consisting of fibers, forms between opposite poles of the cell.

20. Prophase Plant Cell Animal Cell Spindle fibers Centrioles
Photographs from:

21. Metaphase
During metaphase, the chromosomes move toward the middle of the cell and line up at the cell equator (midline).

22. Metaphase Plant Cell Animal Cell
Photographs from:

23. Anaphase
During anaphase, the double-stranded chromosome separates and move to opposite poles of the cell.
There is a complete set of chromosomes at each pole of the cell.

24. Anaphase Plant Cell Animal Cell
Photographs from:

25. Telophase and Cytoplasmic Division
The last stage of mitosis is telophase.
In telophase, a nuclear membrane forms around each set of chromosomes, forming two identical nuclei.
At the end of mitosis, the cytoplasm divides, forming two new identical daughter cells.

26. Telophase Plant Cell Animal Cell
Photographs from:

27. The Cell Cycle

28. Animal Mitosis -- Review
Interphase                                                             
Prophase                                                             
Metaphase                                                             
Anaphase                                                             
Telophase                                                             

29. Plant Mitosis -- Review
Interphase                                                             
Prophase                                                             
Metaphase                                                             
Anaphase                                                             
Telophase                                                             

30. Meiosis
The process of meiosis involves two cell divisions and produces cells that are different from the parent cell.
Meiosis produces cells that have one-half the number of chromosomes as the parent cells.
If meiosis did not take place, the fertilized egg would have double the amount of chromosomes it needs.
Meiosis produces the cells that are needed for sexual reproduction (egg cells and sperm cells).

31. Meiosis
One-half the number of chromosomes is called the haploid, (or n) number.
In humans, the haploid number (n) is 23.
When the egg and sperm unite during fertilization, the species normal chromosome number called the diploid or (2n) number is restored (brought back).
The diploid number in humans is 46.
n (sperm) + n (egg) = 2n

33. Comparison of Mitosis and Meiosis
Characteristic
Mitosis
Meiosis
Number of daughter cells 2 4
Number of cell division 1
Daughter cells are diploid or haploid
Diploid
Full set of chromosomes
Haploid
Half the chromosomes
Daughter cells are identical or different
Identical
Different
Parent cell is diploid or haploid

34. Boy or Girl? The Y Chromosome “Decides”

35. DNA
Structure

36. DNA Structure
DNA consists of two molecules that are arranged into a ladder-like structure called a Double Helix.
A molecule of DNA is made up of millions of tiny subunits called Nucleotides.
There are four types of nitrogenous bases.

37. Nucleotides A
Adenine T
Thymine C
Cytosine G
Guanine

38. Nucleotides Each base will only bond with one other specific base.
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Form a base pair.
Form a base pair.

39. A C T G G A T C

40. DNA Structure
To crack the genetic code found in DNA we need to look at the sequence of bases.
The bases are arranged in triplets called codons.
A G G - C T C - A A G - T C C - T A G
T C C - G A G - T T C - A G G - A T C

41. DNA Structure A gene is a section of DNA that codes for a protein.
Each unique gene has a unique sequence of bases.
This unique sequence of bases will code for the production of a unique protein.
It is these proteins and combination of proteins that give us a unique phenotype.

42. DNA
Gene
Protein
Trait