Question

could you have codons without exons

Answer 1

I think there are(may be) codons which are not exons.
A codon region(part of a codon) becomes an exon when it can code(capable) for an amino acid.
An exon is the coding region of the RNA codon and an intron is the non coding region of an RNA codon.
Think of a stretch of RNA codon which can't code for a peptide, it may be called a codon without exons.

In many genes, each exon contains part of the open reading frame (ORF) that codes for a specific portion of the complete protein.Some mRNA transcripts have exons with no ORFs and, thus, are sometimes referred to as non-coding RNA.
http://en.wikipedia.org/wiki/Exon#Function

Answer 2

yea!i guess!but they would nt code fr anything!they may be introns!nt sure

Answer 3

hakkunamatata, what, i belieive, you are saying is that some introns actually sneak out of the nucleus with the mrna to become non coding regions of a rna codon...because intially introns are not supposed to leave the nucleus.....and are you also saying that if a codon cannot code for a peptide then the introns were present in that region not the exons

Answer 4

You can have codons without exons, for example bacteria do not have exons or introns. Just mRNA.

Introns do leave the nucleus. if you have some stretch of DNA:
start ----A----B----C---D--- end
that is transcribed to RNA

----A----B----C---D---

where the letters are exons and the -'s are introns, all of it will leave the nucleus as above.

After it leaves the nucleus the RNA is processed into mRNA, introns are cut out and some flags are put at the beginning and end of the RNA.

so you end up with an mRNA that looks like:

ABCD

A codon is just any 3 leter chunk of DNA that encodes for an amino acid, in prokaryotes all codons are in exons, but in bacteria don't have exons, but they still have codons.

Answer 5

i understand to some extent but the statement about prokaryotes having exons on the mrna codon and bacteria not having exons but having a codons is a discrepancy to me because bacteria are prokaryotes too. And i dnt think the introns leave the nucleus for eukaryotic cells...(check on that).....dnt forget that the primary transcript is suppose to become processed WHILE in the nucleus before leaving the nucleus for protein synthesis..

Answer 6

I mistyped, eukaryotes have introns, while bacteria do not.
There is processing both inside and outside of the nucleus. But you are right alternative splicing occurs inside the nucleus.

Anyway, bacteria don't have exons or introns, but still have codons.

Answer 7

i find it weird and paradoxical that bacteria dnt have introns nor do thay have exons.. i know that prokaryotes dnt have a nucleus so its really a one step process for protein synthesis in bacteria because while its DNA instructions is being transcribed into RNA, the ribosome attaches to the leading strand of the mrna thats in the making...my question now is does the DNA of a bacterium have exons and introns on the gene? and if so, how is it removed so quickly if they are no additional processing since there is no nucleus

Answer 8

In bacteria there are no exons, the entire gene is one continuous unit. That is how the ribosome can immediately attach and start translation, the RNA is not processed at all. Archea, a different class of prokaryotes, DO have introns unlike bacteria however. So in these organisms the RNA is processed (i.e. the introns are cut out) before translation.

Answer 9

THANK YOU..BUT IF ACHEA ARE PROKARYOTES THEN WHY DO THEY DEFY ABSENCE OF INTRONS IN THEIR DNA...IT WOULD LOOK LIKE AS IF THEY HAVE A NUCLEUS TO REMOVE SUCH LONG INTERVENING SEQUENCES(INTRONS).. AND IF THEY DNT HAVE A NUCLEUS, HOW DO THEY DO IT SO FAST(REMOVAL OF INTRONS) BEFORE THE RIBOSOME READS THE BASES OF THE INTRONS...SOMETHING IS NOT VIVID