How do our cells know where to stop multiplying - i.e. how do they know how to shape a finger or a nose?

Question

When we grow, our cells multiply to form new features, but how do they know where the boundaries are? What stops them from continuing to multiply and what allows them to make the lovely shapes of our bodies?

Answer 1

A bit tricky to answer...
One factor is the following:
Most cells by default will undergo programmed cell death (apoptosis) unless they receive a chemical signal not to.
Cells which don't have access to blood will not be able to get nutrients or the signal to prevent them from apoptosis so they'll die. In order for cells to proliferate again they need to be stimulated by hormones so by controlling distribution, access to, and levels of receptors for those hormones you can achieve some pattern formation.

This is an over-simplified and only partial explanation but I think it is good food for thought.

Answer 2

No one knows the answer to this. This is an active area of scientific research. One clue comes from HOX genes that are important to body patterning during embryogenesis. Mutated HOX genes can cause limb mutations, or even a leg growing where an eye should be (in flies).

Answer 3

God caused that to happen when He created us. Check it out!

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DNA Double Helix: A Recent Discovery of Enormous Complexity
The DNA Double Helix is one of the greatest scientific discoveries of all time. First described by James Watson and Francis Crick in 1953, DNA is the famous molecule of genetics that establishes each organism's physical characteristics. It wasn't until mid-2001, that the Human Genome Project and Celera Genomics jointly presented the true nature and complexity of the digital code inherent in DNA. We now understand that each human DNA molecule is comprised of chemical bases arranged in approximately 3 billion precise sequences. Even the DNA molecule for the single-celled bacterium, E. coli, contains enough information to fill all the books in any of the world's largest libraries.

DNA Double Helix: The "Basics"
DNA (deoxyribonucleic acid) is a double-stranded molecule that is twisted into a helix like a spiral staircase. Each strand is comprised of a sugar-phosphate backbone and numerous base chemicals attached in pairs. The four bases that make up the stairs in the spiraling staircase are adenine (A), thymine (T), cytosine (C) and guanine (G). These stairs act as the "letters" in the genetic alphabet, combining into complex sequences to form the words, sentences and paragraphs that act as instructions to guide the formation and functioning of the host cell. Maybe even more appropriately, the A, T, C and G in the genetic code of the DNA molecule can be compared to the "0" and "1" in the binary code of computer software. Like software to a computer, the DNA code is a genetic language that communicates information to the organic cell.

The DNA code, like a floppy disk of binary code, is quite simple in its basic paired structure. However, it's the sequencing and functioning of that code that's enormously complex. Through recent technologies like x-ray crystallography, we now know that the cell is not a "blob of protoplasm", but rather a microscopic marvel that is more complex than the space shuttle. The cell is very complicated, using vast numbers of phenomenally precise DNA instructions to control its every function.

Although DNA code is remarkably complex, it's the information translation system connected to that code that really baffles science. Like any language, letters and words mean nothing outside the language convention used to give those letters and words meaning. This is modern information theory at its core. A simple binary example of information theory is the "Midnight Ride of Paul Revere." In that famous story, Mr. Revere asks a friend to put one light in the window of the North Church if the British came by land, and two lights if they came by sea. Without a shared language convention between Paul Revere and his friend, that simple communication effort would mean nothing. Well, take that simple example and multiply by a factor containing many zeros.

We now know that the DNA molecule is an intricate message system. To claim that DNA arose by random material forces is to say that information can arise by random material forces. Many scientists argue that the chemical building blocks of the DNA molecule can be explained by natural evolutionary processes. However, they must realize that the material base of a message is completely independent of the information transmitted. Thus, the chemical building blocks have nothing to do with the origin of the complex message. As a simple illustration, the information content of the clause "nature was designed" has nothing to do with the writing material used, whether ink, paint, chalk or crayon. In fact, the clause can be written in binary code, Morse code or smoke signals, but the message remains the same, independent of the medium. There is obviously no relationship between the information and the material base used to transmit it. Some current theories argue that self-organizing properties within the base chemicals themselves created the information in the first DNA molecule. Others argue that external self-organizing forces created the first DNA molecule. However, all of these theories must hold to the illogical conclusion that the material used to transmit the information also produced the information itself. Contrary to the current theories of evolutionary scientists, the information contained within the genetic code must be entirely independent of the chemical makeup of the DNA molecule.

DNA Double Helix: Its Existence Alone Defeats any Theory of Evolution
The scientific reality of the DNA double helix can single-handedly defeat any theory that assumes life arose from non-life through materialistic forces. Evolution theory has convinced many people that the design in our world is merely "apparent" -- just the result of random, natural processes. However, with the discovery, mapping and sequencing of the DNA molecule, we now understand that organic life is based on vastly complex information code, and such information cannot be created or interpreted without a Master Designer at the cosmic keyboard.

Answer 4

It's in the DNA. If you lose your nose, and the surgeon grafts skin and flesh from your butt, the cells actually know they are not on the butt any more, but on the nose, and they build themselves appropriately.

It's all in your DNA, the most amazing molecule in the universe.

Answer 5

I'm not sure but isn't that part of the job of the DNA? The DNA provides all of the information on how we are supposed to look and everything like that right?

Answer 6

the answer lies in the masters perfect touch.

Answer 7

Hormones, I think.

Answer 8

http://en.wikipedia.org/wiki/Cell_%28biology%29#Cell_growth_and_metabolism

Answer 9

DNA