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.
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