1. Unit:
The Cell Cycle 1

2. Phases of the Cell Cycle
Interphase
G1: cell grows and prepares for DNA duplication
S: Synthesis
DNA duplicates
G2: More growth
M Phase (Division)
Mitosis
Nucleus divides
Cytokinesis
Cytoplasm divides

3. What is the difference between:
DNA: chain of nucleotides
Chromatin: uncoiled DNA
Chromosomes: tightly packaged chromatin (DNA)

4. Chromosomes Each chromosome contain 100s-1000s of genes
A gene is a section of DNA that codes for a protein (which determine our physical traits)
In eukaryotes, chromosomes exist in homologous pairs, inheriting 1 from each parent
Homologous pairs carry genes for the same traits

5. How many chromosomes? Example:
Humans have 23 pairs of chromosomes, or 46 total chromosomes, in all body cells (somatic cells)
46 = 2n = diploid (TWO SETS of chromosomes, 1 from mom & 1 from dad)
The exception to the rule are sperm and egg (gametes), which have only 1 copy of each chromosome
23 = n = haploid (1 set of chromosomes)

6. Copying the chromosomes
All DNA in a cell must be copied completely before dividing
(Remember chromosomes are in pairs)
Single copies look like an “I”
Replicated copies look like an “X”
Known as sister chromatids
Attached at the centromere
Both of these pictures represent 2 chromosomes (not 4!)

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8. Mitosis
Cell division to produce two cells that are identical to the parent cell and each other
When:
Growth
Repair
Asexual Reproduction

9. Phases of Mitosis
The four phases of mitosis describe how the chromosomes and nucleus divide
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis is the division of the entire cell (cytoplasm); this occurs directly after telophase

10. Interphase (not mitosis!)

11. Interphase (not mitosis!)
Nuclear
envelope
Chromatin
Centrioles
Not seen: cell grows and replicates DNA to prepare for division

12. Prophase

13. Prophase Centrioles move to opposite sides of cell Spindle fibers form
Organelles have
replicated
Nuclear
envelope
breaks down
Chromosomes
condense; sister
chromatids join

14. Metaphase

15. Metaphase Sister chromatids line up in middle, and are attached to the
spindle

16. Anaphase

17. Anaphase Sister chromatids are pulled apart to opposite poles;
Each side will have the identical DNA

18. Telophase

19. Telophase Spindle breaks down Nuclear envelope reforms
Chromosomes uncoil

20. Cytokinesis (following mitosis!)

21. Cytokinesis (following mitosis!)
Notice the cell will be
in Interphase again
Animal cells - cell membrane pinches off
(cleavage furrow)
Plant cells - cell wall forms between
(cell plate)

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