1. Cell Division: MITOSIS

2. Genes and Chromosomes
Humans have 46 chromosomes in all body cells (somatic cells)
You have 23 pairs of homologous chromosomes
The two chromosomes in the pair look similar and contain genes which affect the same characteristics (2 different alleles)

3. Some cells don’t have any DNA at all
All of your somatic cells are diploid—they have chromosomes which are in homologous pairs
Some cells don’t have any DNA at all
Red blood cells

4. Anatomy of a Chromosome

7. Check your Understanding
How many chromosomes do human cells have?
How many pairs of chromosomes do human cells have?
What are somatic cells?
You have one gene for blue eyes and one gene for brown eyes.
Where did these genes come from?
What are the 2 forms of this gene called?
What does diploid mean?
What are the two halves of a single chromosome called?
What structure holds the chromatids together?
What is a gene?

8. How Eukaryotic Cells Divide
Cell spends most of its time in interphase –not dividing, just doing its job
DNA is stretched out into long, thin chromatin strands
Before division, each chromosome is copied exactly—replication
Nucleus divides and each daughter cell gets a full set of chromosomes
This is called mitosis

9. Stages of Mitosis Prophase
Chromosomes become visible as they coil up and get shorter and thicker
Nuclear membrane disappears
Centrioles move to opposite sides of the cell
Spindle fibers appear and shoot out from centrioles

11. Metaphase Chromosomes line up in center of cell
Spindle fibers attach to each chromosome

13. Anaphase Sister chromatids are pulled apart
Chromatids are reeled to opposite sides of the cell by spindle fibers

15. Telophase Nuclear membrane appears around each set of chromosomes
Chromosomes unwind and go back to being chromatin

17. Cytokinesis Whole cell divides in half
Each daughter cell has an exact duplicate of the DNA
Each daughter cell has 46 chromosomes
Each daughter cell is diploid—23 pairs of chromosomes

19. Check your Understanding
How are the terms DNA, chromatin, chromosome, and genes related?
What is the name of the process by which DNA is copied?
Name, in order, the 6 stages of the cell cycle, starting with the phase cells are in most of the time
Name the phase of the cell cycle where:
Chromosomes line up in the middle of the cell
Chromosomes first become visible
Spindle fibers first appear
Spindle fibers attach to sister chromatids
Centrioles move to opposite sides of the cell
Sister chromatids get pulled apart

20. Still checking…
Nuclear membrane disappears
Nuclear membrane reappears
Entire cell divides in half
No chromosomes are visible
How many daughter cells are created from one parent cell?
How many chromosomes does each daughter cell have?
How many pairs of chromosomes does each daughter cell have?
What is the ploidy of the daughter cells?

21. 1: interphase
2: late interphase / beginning prophase
3: early prophase
4: mid prophase
5: late prophase
6: metaphase
7: late metaphase / early anaphase
8: anaphase
9: early telophase
10: late telophase / cytokinesis

22. VOCABULARY TERMS Somatic Homologous Alleles Diploid Centromere Gene
Chromatid
chromosome
Interphase
Chromatin
Replication
Daughter cells
Mitosis
cytokinesis