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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! Another scientist, named Rosalind Franklin, had been shooting X-rays at blobs of DNA and taking pictures of the patterns the X-rays made. From her pictures, she could tell that their early guesses were wrong. Then Watson and Crick saw one of her pictures, and it gave them an idea. 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. Watson and Crick didn’t give Franklin credit for her help. And by 1962 she had died—and the Nobel Prize is only given to living people.
Pronunciation: 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
If you uncoiled all the DNA from one human cell, it would measure:
two inches long
six inches long
six feet long
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
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.
