Download RNA Structure and Function

RNA Structure and Function
I RNA
A. Def- Ribonucleic acid.
B. Components
1. Ribose, a sugar
2. Phosphate, a negatively charged group
3. Nitrogenous base, a complex organic structure that sits “away” from the
sugar and phosphate
Phosphate
Nitrogenous
Bases
Sugar
C. Nitrogenous bases- Types
1. Adenine
2. Guanine
3. Uracil (in RNA), Thymine (in DNA)
4. Cytosine
D. Functions of RNA
1. The RNA represents a copy of a small segment of the information
contained within the DNA. It is convenient to view the DNA as a giant “recipe book” that
contains all of the information necessary to “make” the organism in which it is found.
The “recipes” each specify the ingredients and their order of addition to make a needed
protein. The protein “ingredients” are the 20 amino acids that serve as sub units of all
proteins.The RNA is then a “xerox copy” of a single recipe within the book. This copy
can then be transferred to the location within the cell where proteins are made.
2. This system allows the DNA to be held in a protected area of the cell,
yet still be used. It is analogous to a “reference book” within a library. The information
must be copied from the master copy to be removed from the protective location and used
in a remote location.
3. The information is contained within the order of nitrogenous bases
along the RNA strand. The sugar/ phosphate string functions to “hold” the “letters” (N
bases) in the proper order to spell out the recipe for the protein to be made. The N bases
are the letters in the genetic code and the sugar/phosphate backbone is the “paper” on
which the code is “written”.
E. Types of RNA
1. Messenger RNA (mRNA)
a. Encodes a protein
b. refers to the “recipe copies” discussed above.
2. Ribosomal RNA (rRNA)
a. A structural component of the cellular machinery that “reads”
the code contained on a messenter RNA
b. Does NOT encode a protein
3. Transfer RNA (tRNA)
a. Functions as a “carrier” of amino acids into the portion of the
cell where the “recipe” is being decoded and the specified protein
is being built.
b. Does NOT encode a protein
F. Comparisons between DNA and RNA
DNA
RNA
Found in the nucleus of Eukaryotic cells or
the nucleoid region of prokaryotic cells
Contains deoxyribose as the sugar in its
backbone
Contains the nitrogenous base thymine as a
letter in the code
Contains all of the information necessary to
manufacture an entire organism
Found primarily within the cytoplasm of all
cells
Contains ribose as the sugar in its backbone
Double stranded helical structure
Stable- Does not degrade easily
Contains the nitrogenous base uracil as a
letter in the genetic code
Contains a small sub set of information
from the DNA. This subset of information
is usually the code that directs the
manufacture of a single protein. (mRNA)
Single stranded structure with occasional
“folding back” upon itself
Unstable- Degrades readily
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G. Processes that employ RNA within the cell
1. Transcription- Manufacture of RNA from a DNA template
2. Translation- manufacture of a protein using the information contained
within a mRNA molecule
H. Handling RNA in the lab
1. Sterile techniques must be applied
2. No contact with skin, body fluids or unsterile surface. All skin and body
fluids (saliva, tears, etc.) contain enzymes that degrade RNA.
I. Important research uses for RNA
1. Reverse transcriptase reading to make “clonable” genes.
2. Marker for gene expression- Genes that are “turned on” will be actively
manufacturing RNA molecules that are “copying” them.
3. Regulation of gene expression through small interfering RNA
molecules
II. Links for further exploration of RNA structure and function.
http://www.web-books.com/MoBio/Free/Ch3C.htm
http://www.ncc.gmu.edu/dna/rna.htm
http://www.ncc.gmu.edu/dna/mRNAanim.htm requires shockwave
http://www.pwc.k12.nf.ca/wadey/biotech/dna1.swf Construction of a DNA
molecule
http://www.pbs.org/wgbh/aso/tryit/dna/shockwave.html Click and drag game for
transcription and translation