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MOLECULAR GENETICS
RIBONUCLEIC ACID (RNA)
Distribution
Found all
over the cell (nucleus, mitochondria, chloroplasts,
ribosomes and the soluble part of the cytoplasm)
Types
Messenger
RNA (mRNA) <5%
Ribosomal RNA (rRNA) Up to 80%
Transfer RNA (tRNA) About 15%
In
eukaryotes small nuclear ribonucleoproteins (snRNP)
Structure
Single
polynucleotide strand which may be looped or coiled
(not a double helix).
Sugar Ribose (not deoxyribose).
Bases used: Adenine, Guanine, Cytosine and
Uracil (not
Thymine).
mRNA
A
long molecule 1 million Daltons
Ephemeral
Difficult to isolate
mRNA provides the plan for the polypeptide chain. |
rRNA
Coiled |
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Two
subunits: |
a
long molecule 1 million Daltons
a
short molecule 42 000 Daltons |
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Fairly stable
Found in ribosomes
Made as subunits in the nucleolus
rRNA provides the platform from protein synthesis |
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tRNA
Short molecule about 25 000 Daltons
Soluble
At least 61 different forms each has a specific
anticodon as part of its structure.
tRNA translates the message on the mRNA into a
polypeptide chain. |
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© Paul Billiet 2012 |
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