1. KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions.

2. Formation of new cells by cell division
All organisms undergo cell division for three main reasons.
Growth and development
Repair
Reproduction
Most eukaryotic cells use mitosis and cytokinesis for growth, development, repair and asexual reproduction.
Bacteria use binary fission for asexual reproduction
Mitosis is never used for sexual reproduction, that requires meiosis.

3. Cells divide at different rates.
The rate of cell division varies with the need for those types of cells.
Some cells are unlikely to divide (G0).

4. Chromosomes condense at the start of mitosis.
DNA wraps around proteins (histones) that condense it.
DNA double helix
DNA and histones
Chromatin
Supercoiled DNA

5. DNA plus proteins is called chromatin.
chromatid
telomere
centromere
One half of a duplicated chromosome is a chromatid.
Sister chromatids are held together at the centromere.
Telomeres protect DNA and do not include genes.
Condensed, duplicated chromosome

6. The cell cycle has four main stages.
The cell cycle is a regular pattern of growth, DNA replication, and cell division.

7. The main stages of the cell cycle are gap 1, synthesis, gap 2, and mitotic phase.
Gap 1 (G1): cell growth and normal functions
DNA synthesis (S): copies DNA
Gap 2 (G2): additional growth
Mitotic phase(M): includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis)

8. There are three different checkpoints that can stop mitosis.
G1 Checkpoint: The checkpoint decides whether S phase will happen. S phase will only happen if the cell is healthy and large enough.
G2 Checkpoint: Checks that DNA replication happened ok.
M Phase Checkpoint: Checks that mitosis has occurred properly.

9. Mitosis and cytokinesis produce two genetically identical daughter cells.
Parent cell
centrioles
spindle fibers
centrosome
nucleus with
DNA
Interphase prepares the cell to divide.
During interphase, the DNA is duplicated.

10. Mitosis divides the cell’s nucleus in four phases.
During prophase, chromosomes condense and spindle fibers form.

11. Mitosis divides the cell’s nucleus in four phases.
During metaphase, chromosomes line up in the middle of the cell.

12. Mitosis divides the cell’s nucleus in four phases.
During anaphase, sister chromatids separate to opposite sides of the cell.

13. Mitosis divides the cell’s nucleus in four phases.
During telophase, the new nuclei form and chromosomes begin to uncoil.

14. Cytokinesis differs in animal and plant cells.
In animal cells, the membrane pinches closed.
In plant cells, a cell plate forms.

15. Binary fission is similar in function to mitosis.
Asexual reproduction is the creation of offspring from a single parent.
Binary fission produces two daughter cells genetically identical to the parent cell.
Binary fission occurs in prokaryotes.
parent cell
DNA
duplicates
cell begins
to divide
daughter
cells

16. Environment determines what form of reproduction is most advantageous.
Asexual reproduction is an advantage in consistently favorable conditions.
Sexual reproduction is an advantage in changing conditions.

17. Some eukaryotes reproduce through mitosis.
Budding forms a new organism from a small projection growing on the surface of the parent.
bud
Hydra
Yeast

18. Fragmentation is the splitting of the parent into pieces that each grow into a new organism.
Vegetative reproduction forms a new plant from the modification of a stem or underground structure on the parent plant.

19. You have body cells and gametes.
Body cells are also called somatic cells.
Germ cells develop into gametes.
Germ cells are located in the ovaries and testes.
Gametes are sex cells: egg and sperm.
Gametes have DNA that can be passed to offspring.
body cells
sex cells (sperm)
sex cells (egg)

20. Your cells have autosomes and sex chromosomes.
Your body cells have 23 pairs of chromosomes.
Homologous pairs of chromosomes have the same structure.
For each homologous pair, one chromosome comes from each parent.
Chromosome pairs 1-22 are autosomes.
Sex chromosomes, X and Y, determine gender in mammals.

21. Body cells are diploid; gametes are haploid.
Fertilization between egg and sperm occurs in sexual reproduction.
Diploid (2n) cells have two copies of every chromosome.
Body cells are diploid.
Half the chromosomes come from each parent.

22. Haploid (n) cells have one copy of every chromosome.
Gametes are haploid.
Gametes have 22 autosomes and 1 sex chromosome.

23. Chromosome number must be maintained in animals.
Many plants have more than two copies of each chromosome.
Mitosis and meiosis are types of nuclear division that make different types of cells.
Mitosis makes more diploid cells.

24. Meiosis makes haploid cells from diploid cells.
Meiosis occurs in sex cells.
Meiosis produces gametes.