Cell Biology · Lesson 12 of 12
Specialized Cells
A printed script for a school play sits on a kitchen table. Every student in the cast gets the very same booklet. The student playing the detective highlights their own lines in yellow. The student playing the baker marks a completely different set of lines in blue. Nobody needs to read every single line out loud to put on the play. Each person just reads the part they were given.
Almost every cell in your body carries the same DNA. A nerve cell, a muscle cell, and a skin cell differ because each one switches on a different set of genes and leaves the rest switched off. That's how your body builds about two hundred kinds of cells from one set of instructions. The idea that cells have "Same instructions, different jobs" isn't true for every single cell, though. Mature red blood cells toss their nuclei away to carry oxygen, and egg and sperm cells carry only half the set. Some immune cells even cut and rearrange their DNA to build antibodies.
Therefore
When you see two body cells that look nothing alike, don't assume they have different genes. Ask instead which parts of the shared manual each cell switches on.
John Gurdon and Shinya Yamanaka, 1962 and 2006
In 1962, John Gurdon worked at Oxford with African clawed frogs. People thought specialized cells lost the genes they didn't use. Gurdon took the nucleus from a tadpole's gut cell and put it into a frog egg whose nucleus had been destroyed. That egg grew into a normal swimming tadpole. That proved the gut cell still carried all the instructions. His old school report from Eton had called his dream of becoming a scientist quite ridiculous. In 2006 at Kyoto University, Shinya Yamanaka added four genes to mouse skin cells and turned them back into flexible stem cells. Gurdon and Yamanaka shared the Nobel Prize in 2012.
A small reminder, on a notebook or a desk lamp, that your nerve and muscle cells read from the very same book.
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Related patterns
pairs with
Nucleus — Where the Instructions Are Kept
The nucleus holds the full DNA manual that each specialized cell selectively reads.
contrasts with
Mitosis — Coil, Line Up, Pull Apart, Split
Mitosis copies the instructions exactly, but specialized cells do very different work.
extends to
Cell Theory — Every Cell Comes From Another Cell
Your body starts from one dividing cell and ends with hundreds of cell types.