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Name: Robert W.
Status: Educator
Age: 30s
Location: N/A
Country: N/A
Date: April 2004


Question:
Counting the number of protein-encoding genes in the human genome is a difficult process, as the "start" and "stop" boundaries of transcribed genes are only imperfectly understood. Some researches have taken a different approach, capturing mRNAs from the cytoplasm and matching them with the human genome DNA sequence. They report finding upward of 65,000 discrete mRNA-transcribing sequences in the genome. does this mean that there are actually 65,000 human genes, rather than the 30,000 originally reported?



Replies:
It IS very complicated. I was in a genetics seminar a few years ago and we spent an hour and a half trying to come up with a new definition for a gene. Recall that transcripts are edited before they leave the nucleus and that introns are removed and exons are spliced together. One way of making the most of the genome is to splice different exons together from within the same "gene". By capturing different mRNA's from the cytoplasm researchers can see how many of these transcripts are active in different kinds of cells. So I wouldn't say there are actually twice as many "genes", but more ways to make the most of the "genes" we have.

vanhoeck



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