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Name: katie
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Question:
What are the possible biological roles of the cap and poly-A tail in mRNA?


Replies:
Katie,

Experiments have clearly shown that the poly-A tail on a mRNA is to prevent it from being dismantled in the cytosol of the cell by enzymes when it leaves the nucleus. RNAs without this tail are quickly dismantled and with the string of A's[as many as 200!], may last for 24 hours or more. The modified guanine nucleotide at the head of the messenger RNA [mRNA] identifies the molecules as a mRNA. It is a chemical signal as to what the molecule's function is to be. The other two types of RNA [ribosomal RNA(rRNA) and transfer RNA (tRNA)] appear to have chemical signaling to indicate their function as well. However, I must note that this chemical signaling has not be demonstrated conclusively as yet. Feb. 2000

Steve Sample


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