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Name: Will
Status: Student
Grade:  6-8
Location: N/A
Country: United States
Date: Spring 2010

If an embryo is a living cell or group of cells how is it possible to freeze them and then bring them back to life?

There are a number of features which would make it possible to freeze an embryo when it would not be possible to freeze a mouse for instance and bring it back to life.

First an embryo is very small - about the size of a full stop - or Period in USA. Something that small will freeze very quickly, where the size of the mouse means that the skin would be frozen long before the inner organs were fully cold. The mouse would die because the heart would be trying to pump blood through frozen skin vessels.

Which brings us to the second difference - the presence of blood and other liquids. You know that water expands when it freezes. That is why ice floats!. In your veins freezing blood would expand and tear the walls of the vein. If you could be defrosted your blood would leak out of the torn blood vessels and you would bleed to death. The same problem would affect your stomach and intestines - your food and 'waste' would leak out - YUCK!!!! An embryo on the other hand is so small it has no need yet for blood and digestive organs or a heart - it is JUST cells - simple ones. If the cells are frozen quickly, the cell walls can stretch enough to accommodate the small increase in size.

Nigel Skelton
Tennant Creek High School

By freezing them in a solution of DMSO, it is possible to freeze them without damaging them. DMSO is dimethyl sulfoxide.

Ron Baker, Ph.D.

Hi Will,

Many, many kinds of cells can be frozen and then thawed and still live -- in fact, freezing cells is a common method of storing cells in scientific research. It sounds like you are implying that something living cannot be frozen and then thawed and still be alive. It's true that freezing whole multicellular organisms typically kills them (for a variety of reasons). And freezing can damage the cells too; not all cells live through freezing and thawing. That said, cells -- and even some tissues -- can be frozen and then thawed and still live.

Hope this helps,

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