This is Cell Biology!!! The length of a particular gene in human DNA, measured f
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Question
This is Cell Biology!!!The length of a particular gene in human DNA, measured from the start site for transcription to the end of the protein-coding region, 8,000 nucleotides, while the length of the mRNA produced from this gene is 2000 nucleotides. What are the possible reasons for this discrepancy?
This is Cell Biology!!!
The length of a particular gene in human DNA, measured from the start site for transcription to the end of the protein-coding region, 8,000 nucleotides, while the length of the mRNA produced from this gene is 2000 nucleotides. What are the possible reasons for this discrepancy?
The length of a particular gene in human DNA, measured from the start site for transcription to the end of the protein-coding region, 8,000 nucleotides, while the length of the mRNA produced from this gene is 2000 nucleotides. What are the possible reasons for this discrepancy?
The length of a particular gene in human DNA, measured from the start site for transcription to the end of the protein-coding region, 8,000 nucleotides, while the length of the mRNA produced from this gene is 2000 nucleotides. What are the possible reasons for this discrepancy?
Explanation / Answer
When we consider a eukaryotic gene that has been transcribed into an mRNA, unlike prokaryotic mRNA it is not functional as soon as it is transcribed. It needs to undergo certain post-transcriptional modification to be fully functional. A eukaryotic gene consists of two regions called introns(non-coding) and exons(coding). For an mRNA to be functional, the non coding region(introns) need to be excised out and the coding regions need to be joined together to form a stretch of functional mRNA. this process, discovered only in the late 1970's, is known as splicing(splice=to cut).
There are two basic mechanism by which a cell would splice the introns of an mRNA; either by forming a spliceosome complex or by self splicing initiated by the intron itself. alternative splicing has also been discovered where a particular mRNA woud be spliced in different techniques and different places and joined in various ways to produce various splice variants from a single mRNA. this is a way or the cell to control gene expression as well.
Hence in eukaryotes, the length of the initial mRNA that would be transcribed from the gene would not be the same as the length of the functional mRNA the is capable of carrying out translation. It will always be shorter than the trancribed mRNA as huge chunks of introns would be editted out from the mRNA.
In the example given above, the length of functional mRNA is just 2000 nucleotides though the initial gene length was 8000bps. Almost 6000 nucleotides worth of intons have been excized.
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