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DNA and RNA are both nucleic acids, but they contain structural differences. DNA and RNA are named for the type of sugars they contain. DNA is made with deoxyribose sugars. RNA is made with ribose sugars. RNA uses uracil bases in place of thymine bases. Uracil and thymine are both pyrimidines.
As in DNA replication, one strand of DNA is used as a guide for determining the sequence of the synthesized bases. Cytosine pairs with guanine, and uracil pairs with adenine. A piece of RNA is complementary to its DNA template. An organism’s DNA is generally double-stranded. The RNA used to make proteins is single-stranded.
The main functional difference between DNA and RNA is that DNA is permanent, while RNA is temporary. When one of Patrick’s tapes is destroyed, he simply makes another copy. However, if the original CD is destroyed, the songs are lost forever. Just as Patrick’s CD collection is his library of music, an organism’s DNA is its library of information.
A cell uses its DNA to make temporary copies of the information as RNA. If the RNA copies are damaged or more are needed, the cell makes more copies. Different cells make different sets of RNAs, depending on which proteins they need. No matter what happens to the RNA, the original information is still available in the DNA.
While there's only one type of DNA, there are three types of RNA, distinguished primarily by function. The RNA that's used as the template to make a protein is called messenger RNA, or mRNA. mRNA is used as the template for translation. Transfer RNA, or tRNA, and ribosomal RNA, or rRNA, are also used in translation. For the rest of this activity, we'll focus on how mRNA is synthesized.
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