Difference Between Introns and Exons
Difference Between Introns and Exons: Introns and Exons are the integrated part of the eukaryotic genome. Introns are intervening non-coding nucleotide sequences whereas the exons are the amino acid coding sequences.
We have seen various evolutionary changes from the prokaryotes to the eukaryotes. The eukaryotic cells have become more advanced and organised as compared to prokaryotes. Although prokaryotes have a higher tendency to evolve faster than eukaryotes, but the level of complexity in a eukaryotic cell is unmatchable.
Difference Between Introns and Exons
Eukaryotes have evolved their genome and have made it more complex by introducing the coding regions (EXON) and the non-coding region (INTRON). The stretch of DNA contains both the introns and the exons, in which exons participate in the translational process (the process of protein formation). In contrast, the introns are the noncoding intervening spacer sequences which are removed further during the RNA processing.
Exons
Exons also called expressing sequences, are the mRNA sequences that get joined during the post-transcriptional modification and code for amino acid sequencing during translation.
Do prokaryotes have exon sequences?
The prokaryotic genome is not as complex as eukaryotes. So, the whole genome of prokaryotic organisms contains only the exon sequences, and no intron sequences can be seen in prokaryotes except a few exceptions.
Introns
Introns are the intervening sequences in the eukaryotic genome between the exon sequences. They do not code for any protein sequences of amino acid sequences as they are removed during the post-transcriptional modifications (occur inside the nucleus).
- The mRNA transcribed during the process of transcription (a process in which the RNA is formed by taking DNA as a template strand) is a premature RNA (called hnRNA ) that undergoes various post-transcriptional modifications to form a mature RNA (mRNA).
- One of the post-transcriptional events is intron splicing, or the removal of intron sequencing to form a mature RNA.
- The introns can be removed by forming a spliceosome complex, or some of the introns have an inbuilt mechanism of removing self from the exons sequence (called self-splicing introns).
- Introns are present in a range of RNAs irrespective of the fact whether they are coding or non-coding introns RNAs; for example, introns are present in mRNA, rRNA, and tRNA.
Introns could be self-splicing or non-self-splicing
Non-self-splicing introns are the introns found in most RNA molecules, and the spliceosome complexes remove them. Whereas the self-splicing introns found in rRNA have the ability to remove them by an intrinsic ability of transesterification reaction.
Difference between Introns and Exons
|
Introns |
Exons |
|---|---|
|
Found only in Eukaryotes (Few exceptions are present in prokaryotes e.g. one of the genes found in Bacillus bacteriophage) |
Found in both the prokaryotes and eukaryotes |
|
Non-coding nucleotide sequences (do not code for any amino acid) |
Codes for the amino acid sequences during the process od transcription |
|
Removed during the post-transcription modifications of hnRNA in order to form a mature mRNA. |
Joined together to form mRNA during the post-transcription modifications of hnRNA in order to form a mature mRNA. |
|
A frequent mutation can be seen in introns; hence are considered less conserved regions |
a few mutations are listed in these regions and are considered the most conserved regions. |
|
A few mature mRNAs contain some intron sequences, hence imparting complexity to the genome. |
Some of the exons may be excluded during the process of post-transcriptional events and hence imparting genome complexity. |
Note: Introns can also code an amino sequence if they are present in mature mRNA. For example, during experimental cases when we clone a eukaryotic gene in a prokaryotic system at that time it can be seen that the introns can also code for the amino acids. It the post-transcriptional modifications which exclude the intron sequence from a mature mRNA and make them non-coding sequences.
FAQs on Introns and Exons
Q1: What is the main difference between introns and exons?
Answer:
The introns and exons can be differentiated on the bases of coding amino acid sequences during protein translational process. Exons are the coding sequences which codes for amino acid sequence during protein synthesis, whereas the introns are intervening non-coding sequence which gets removed during the process of post transcriptional modifications.
Q2: What are the two functions of introns?
Answer:
Following are the functions of introns
- Involved in the regulation of alternative splicing
- Makes eukaryotic mRNA a polycistronic mRNA
Q3: What are introns made of?
Answer:
The introns are as same as exons made up of nucleotide sequences but do not code for the protein sequences as they are removed during the process of post-transcriptional modifications.
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