RNA Structure - Advanced
Douglas Wilkin, Ph.D.
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Printed: October 4, 2016
AUTHOR
Douglas Wilkin, Ph.D.
www.ck12.org
C HAPTER
Chapter 1. RNA Structure - Advanced
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RNA Structure - Advanced
• Describe the structure and function of RNA.
Protein or RNA molecule?
Actually both. This represents the chemical structure of the ribosome of Baker’s yeast, Saccharomyces cerevisiae.
It is made of both protein and RNA. The RNA in this ribosome, though, has protein-like properties. RNAs are able
to fold back onto themselves, folding into three-dimensional structures with functional properties. Sometimes these
are enzymatic properties, such as those found in the ribosome.
RNA Structure
RNA structure differs from DNA structure in three specific ways. Both are nucleic acids and made out of nucleotides; however, RNA is single stranded while DNA is double stranded. RNA nucleotides, like those from DNA,
have three parts: a 5-carbon sugar, a phosphate group and a base. RNA contains the 5-carbon sugar ribose, whereas
in DNA, the sugar is deoxyribose. The difference between ribose and deoxyribose is the lack of a hydroxyl group
attached to the pentose ring in the 2’ position of deoxyribose.
Though both RNA and DNA contain the nitrogenous bases adenine, guanine and cytosine, RNA contains the
nitrogenous base uracil instead of thymine. Uracil pairs with adenine in RNA, just as thymine pairs with adenine in
DNA. Uracil and thymine have very similar structures; uracil is an unmethylated form of thymine.
The nucleotide sequence of RNA, which is complementary to the DNA sequence, allows RNA to encode genetic
information. RNA though carries the genetic information of just one gene. Hence, compared to DNA, RNA
molecules are relatively small.
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A comparison of RNA and DNA is shown in Table 1.1.
TABLE 1.1: short caption
Specific Base
Sugar
Size
Location
Types
RNA
single stranded
contains uracil
ribose
relatively small
moves to cytoplasm
3 types: mRNA, tRNA, rRNA
DNA
double stranded
contains thymine
deoxyribose
big (chromosomes)
stays in nucleus
generally 1 type
MEDIA
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RNA Activity
Analysis of RNAs has revealed that they are highly structured. Unlike DNA, most RNAs, though single-stranded,
do form specific secondary structures. Like proteins, the folded structure of the RNA is specific and gives the RNA
functional properties. Some RNAs contain self-complementary sequences that allow parts of the RNA to fold and
pair with itself to form double helices. RNA nucleotides base-pair like DNA nucleotides, however in DNA, this
base-pairing is necessary to form the double helix structure uniform to all DNA. In RNA, the base pairs would be AU and G-C pairings. The base pairing in RNA is unique to each molecule of RNA and results in a three-dimensional
structure that gives each molecule functional properties. Unlike DNA, their structures do not consist of long double
helices but rather collections of short helices combined into a functional molecule. Because of the structure of RNA,
the RNA molecule can achieve biochemical catalysis, similar to that of enzymes. For instance, the structure of the
ribosome allows peptide bond formation during protein synthesis. The active site of the ribosome is composed
entirely of RNA.
Summary
• RNA is a single-stranded nucleic acid.
• RNA contains the nitrogenous base uracil.
• RNA can fold into three-dimensional structures with functional properties.
Review
1. Describe the differences between DNA and RNA.
2. How does RNA have functional properties?
3. What is the structural difference between uracil and thymine?
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