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088

DNA

OLogy Series
biology
card
088

DNA

OLogy Series
biology

Saying "deoxyribonucleic acid" is a real mouthful. Luckily, you can call it DNA for short. DNA is found in all living things, including YOU! DNA is in every cell of your body and is shaped like a long, twisted ladder. The steps of this "ladder" are made of only four building blocks, called bases. These bases are known by the letters A, C, G, and T.

The Discovery of DNA's Shape
In 1953, after many false starts, James Watson and Francis Crick made a very cool discovery: they figured out the shape of DNA! With the help of some Tinker-Toy-like models, Watson and Crick discovered that DNA is shaped like a twisted ladder. This shape is called a double helix. Shortly after that, scientists discovered how DNA makes a copy of itself. The "steps" of the spiral ladder split in the middle. Then unattached bases inside the cell are attached to each "half ladder." This process creates two identical spiral ladders. When a cell splits, each cell gets one of these "ladders" of DNA. In 1962, Watson, Crick, and their partner Maurice Wilkins won the Nobel Prize for their groundbreaking work.

If you uncoiled all the DNA from one human cell, it would measure:

two inches long

six inches long

six feet long

Are you right?

Correct!

DNA's threads are coiled so tightly that all six feet fit in the nucleus of one human cell, something like the wires in a Brillo pad. Now that's twisted!

What is DNA's job?

to store information

to hold cells together

to keep the chromosomes from fighting

Are you right?

Correct!

When cells "read" the pattern of letters in DNA, they use this information to "decide" how to grow and develop.

It was just a pretty molecule, and that's what made it so exciting.

Deoxyribonucleic acid
(de-oxy-ri-bo-nu-cle-ic acid)
Function: makes up genes, and "junk DNA," stuff we don't yet fully understand
Length in human cell: about 3.2 billion bases
Shape: double helix, a twisted ladder shape
Discoverers of double helix: J. Watson, F. Crick, R. Franklin, and M. Wilkins.
>Significance: contains the genetic information for all living things

Image credits: Kelvin Chan; Kevin Chan.