Dividing body cells use Mitosis • Sex cells use Meiosis • 1 Cell → 2 Clones (PMAT)
The Paper Cut Hook: "If you get a paper cut, how does your skin close up in 3 days? Your healthy skin cells literally photocopy themselves through mitosis to build replacement skin. Mitosis = My-toes-is! It heals your toes, fingers, and stomach lining."
Humans make ~3.8 million cells/secWhen you scrape skin, thousands of cells are destroyed. The surrounding surviving cells receive chemical signals to divide. Each cell makes an exact twin photocopy of itself until the gap is sealed.
Mitosis is for GROWTH and REPAIR.
It is how a baby grows into an adult, and how broken bones or cut skin knit back together. It makes BODY CELLS (Somatic cells). It does not make sperm or egg cells!
You began as 1 single microscopic fertilized cell. Through non-stop mitosis, that single cell cloned itself trillions of times to build muscles, bones, skin, and organs.
"Do you get taller because your cells grow as big as balloons?"
NO! Growth adds many more microscopic cells through mitosis. Cells can also grow and change size; this model keeps their size fixed to show the increase in cell number.
Chromosomes condense and pack tight into visible X-shapes. The nuclear membrane starts dissolving, and centrioles begin building protein spindle fibers.
Four chromosome pairs are shown as a simplified model. Each human body cell has 46 chromosomes.
Mitosis produces clones. There is no mixing of DNA, no crossing over, and no variation. Daughter 1 and Daughter 2 receive the exact same 46 chromosomes as the parent.
The chromosome count does not divide in half! During Interphase, the cell copies all 46 chromosomes. When it splits, each daughter cell gets the full set of 46 chromosomes.
"Can a skin cell divide to create a blood cell or bone cell?"
NO! Mitosis can only clone the exact cell type that divided. A skin cell makes skin cells; a liver cell makes liver cells.
Remember: Mitosis makes new body cells for growth and repair. Meiosis produces sperm and egg cells.
Stomach acid destroys cells constantly. How does the stomach multiply to replace damaged epithelial cells every 5 days?
5 state-standard questions testing chromosome counts, PMAT stages, and body cell replacement.