2 questions concerning RNA

[ramo]

I have two questions about RNA I would like to ask:

1. Why is uracil used in RNA instead of thyamine?

2. Why does a cell never run out of ribnucleotides? I mean where do they come from besides from introns being recycled?

[chintu]

For the first :
Thyamine will give more stability for the strand. if RNA had the thymine it aquires more stability this will affect the synthesis of proteins. i think this is the reason.
i cant understand ur second one.

[DevGrp]

Cells turn over their mRNA quite quickly, some mRNAs only last minutes. So I guess cells recyle their ribonucleotides. They can also synthesis fresh ones as required .

[ramo]

ok i get the first question, but as far as recycling the nucleotides is concerned does the RNA re-enter the nucleus to be recycled after it has been thorugh the ribosomes and made the protein?