Mitosis

Why do cells divide?

cells die & need to be replaced
allows organisms to increase in size

Prokaryotic Chromosomes

double stranded DNA

single round chromosome

replicate through binary fission

Matched pairs

chromosomes from each parent

Homologous

same in size & function

How many chromosomes do humans have?

46

How many match pairs of chromosomes?

22

Female

XX

Male

XY

Somatic cells

cells forming the body of the organism

Reproductive cells / Gametes

sex cells

Cell Cycle

1. Interphase G1

2. S phase

3. Interphase G2

4. Mitosis

5. Cytokinesis

Interphase G1

cell growth & protein synthesis

S phase

DNA & centrosome replication

Interphase G2

further growth & protein synthesis

Mitosis

1. prophase

2. prometaphase

3. metaphase

4. anaphase

5. telophase

Cytokinesis

cytoplasm divided & forms two daughter cells

Red blood cell

replaced every 6 weeks

Intestinal lining cell

replaced every 3 weeks

Brain, heart, muscle cells

rarely divide

Checkpoints

points in cell cycle where progress is blocked

Strategic checkpoints

1. G1 checkpoint: DNA integrity

2. G2 checkpoint: chromosome duplication

3. M checkpoint: attachment kinetochore to spindle fiber

Oncogene-Tumor Suppressor Gene Theory

Oncogenes: accelerator
Tumor Suppressor genes: brakes

Benign

self-contained
can be removed

Malignant

cancerous cells

continuously replicate

Metastasis

spreading of cancer

Apoptosis / Programmed cell death

1. cell detects damaged DNA

2. cell is swallowed by a neighboring cell or a patrolling immune cell