1. Cell Growth and Division

2. Genes Chromosomes contain DNA. Sections of DNA is called Genes.
Genes control specific cell activities and characteristics of every organism.
A human has 46 chromosomes and 50,000 genes.
Some genes control eye color; while others control weight.

3. Cell Division
All cell division is not the same. Cells can divide by mitosis, so each daughter cell retains a full set of chromosomes, or by meiosis, which halves the chromosomes and produces sperm and eggs.

4. Chromosomes
The nucleus controls everything the cell does and is. Inside the nucleus are threadlike structures called chromosomes.
Chromosomes are made up of a chemical called DNA.
The DNA code determines the shape and function of the cell.

5. DNA
Chromosomes contain genes and are made up of DNA. Genes are small sections of chromosomes that determine traits (physical characteristics of an organism). DNA is inside the nucleus of cells and carries the genetic information. This information is passed on from parent to offspring.
The scientific name for DNA is deoxyribonucleic acid.

6. Body Cells
Your body cells are constantly growing, dividing, and dying. This is true for animal cells and plant cells.
Most of the life of any cell is spent in a period of growth and development called interphase. Cells in your body that no longer divide (like nerve and muscle cells) are always in interphase.
When body cells divide it is called Mitosis.

7. Mitosis
Mitosis is the process when the nuclei of body cells split (cell division). This produces two nuclei with the exact same information. It is an EXACT copy of the original.

9. Steps of Animal Mitosis Stage 1: Interphase
Nucleus can be clearly seen.
Chromosomes (structures in the nucleus that contain DNA) cannot be seen but are actively copying themselves.
When the cell is ready to divide the chromosomes become visible. They are thick and double stranded and are held together at a region called a centromere.

10. Steps of Animal Mitosis Stage 2: Prophase
Chromosomes can now be clearly seen.
Nucleolus and nuclear membrane fade and disappear.
Centrioles (cylinder shaped organelles found in the nucleus of a cell) move to opposite ends of the cell.
Between the centrioles, spindle fibers begin to stretch across the cell.

11. Steps of Animal Mitosis Stage 3: Metaphase
Double-stranded chromosomes line up across the center of the cell.
Each centromere attaches to a spindle fiber.

12. Steps of Animal Mitosis Stage 4: Anaphase
Centromeres divide.
Two strands of each chromosome separate.
Separate strands move away from each other toward opposite ends of the cell. (Each ‘daughter cell’ now has an identical set of genes)

13. Steps of Animal Mitosis Stage 5: Telophase
Centrioles and spindle fibers start to disappear.
Chromosomes stretch out and become harder to see.
Nuclear membrane forms around each mass of chromosomes.
New nucleolus appears in each new nucleus.

14. Cell Division- Animal Cells
Once the nucleus has divided, the cytoplasm also separates and two whole new cells are formed.
In animal cells, the cytoplasm pinches in to form the new cells, then the cycle starts all over again.

15. Results of Mitosis Remember- mitosis is the division of a nucleus.
Mitosis produces two new nuclei that have the same number of chromosomes as the original nucleus (human body cells have 46 chromosomes… new body cells will have 46 chromosomes as well).

17. Asexual Reproduction
Your body forms two types of cells- body cells and sex cells.
Sex cells are the egg or sperm in the reproductive organs.
In asexual reproduction new organisms are produced from one parent.
Offspring produced by asexual reproduction have DNA identical to the DNA of the parent organism.

18. Examples of Asexual Reproduction
Planaria regenerating
Hydra budding
Yeast budding
Budding: asexual reproduction in which a new organism grows from the body of the parent organism
Regeneration: asexual reproduction in which an organism repairs damaged or lost body parts
Fission: asexual reproduction in which organism divides into two equal parts

19. Examples of Asexual Reproduction (II)
Newt limb regeneration
Sponge regeneration
Sea star regeneration
Bacteria fission
Spider plant runner
Strawberry plant runner

20. Sexual Reproduction and Meiosis
In sexual reproduction a new organism is produced when sex cells from two parents combine.
The sex cell from the male parent is called the sperm.
The sex cell from the female parent is called the egg.
Meiosis is the process of nuclear division that produces sex cells (takes place in reproductive organs of both plants and animals).

21. Importance of Sex Cells
Human sex cells have 23 chromosomes, not 23 pairs of chromosomes. Sex cells are haploid (contain only one chromosome from each pair).
A cell that has two of every kind of chromosome is diploid. Body cells which have 23 pairs of chromosomes are diploid.

22. Fertilization
The joining of an egg and a sperm is called fertilization.
The cell that forms in fertilization is called a zygote.
A zygote has 46 chromosomes and is, therefore, diploid.

23. Meiosis
In meiosis there are two divisions of the nucleus, meiosis I and meiosis II.

24. Meiosis I
Prophase I
double-stranded chromosomes and spindle fibers appear.
Nuclear membrane and nucleolus disappear.
Like chromosomes come together in matching pairs.

25. Meiosis I
Metaphase I
Pairs of chromosomes line up in the center of the cell.
Centromeres attach to spindle fibers.

26. Meiosis I Anaphase I Double-stranded chromosomes separate.
Chromosomes are pulled to opposite ends of the cell.

27. Meiosis I Telophase I Cytoplasm divides and two cells form.
Each chromosome is still double-stranded.

28. Meiosis II
Prophase II
Double-stranded chromosomes and spindle fibers reappear in each new cell.

29. Meiosis II Metaphase II
Double-stranded chromosomes move to center of cell.
Centromeres attach to spindle fibers.

30. Meiosis II Anaphase II Centromere divides.
Two strands of each chromosome separate and move to opposite ends of the cell.

31. Meiosis II Telophase II Spindle fibers disappear.
Nuclear membrane forms around the chromosomes at each end of the cell.
Each nucleus contains half the number of chromosomes that were in the original nucleus. (23 single-stranded chromosomes for human body cells).

32. End Product

36. Comparing Mitosis and Meiosis
Feature
Mitosis
Meiosis
What type of cell
Body cell
Sex cell
Beginning cell
Diploid
Number of cells produced
Two
Four
End-product cell
Haploid
Number of chromosomes produced
Same as parent- 46
Half the parent cell number- 23
Type of cell (body, sex); beginning cell (diploid, diploid), #cells produced (2,4); end-product (diploid/haploid); #chromosomes produced (46, 23)