tag:blogger.com,1999:blog-37148773.post6267442493978039557..comments2024-03-27T14:50:47.345-04:00Comments on <center>Sandwalk</center>: How Many Genes Do We Have?Larry Moranhttp://www.blogger.com/profile/05756598746605455848noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-37148773.post-26312082016338019112014-01-16T04:35:42.852-05:002014-01-16T04:35:42.852-05:00We can afford to be human centrists because only h...We can afford to be human centrists because only humans are doing this work, and consciously modifying genes in a way that is "utterly foreign" to natural selection as Richard Dawkins reminds. By the very act of using human created technology and commenting on this dimension of difference totally unique to humans, human centrism will continue, because it's a truth, it's what we do with that truth that is important. We have a control over the natural world beyond parallel with all other life, but we need to take control of that control.Mark Cowanhttps://www.blogger.com/profile/07579240891951328334noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-74182922609311973712007-03-24T15:58:00.000-04:002007-03-24T15:58:00.000-04:00Rosie Redfield says,That definition is probably sa...Rosie Redfield says,<BR/><BR/><I>That definition is probably satisfactory for first-year university biology courses, but I don't think it's very satisfactory when applied to the question of how many human genes there are.</I><BR/><BR/>It's perfectly satisfactory. There are exceptions.<BR/><BR/><I>The question of 'how many human genes there are' arises because we want to know how many distinct gene products are needed to specify humans, not how many distinct transcripts our DNA produces.</I><BR/><BR/>Well, <B>some</B> people may be interested in the total number of protein variants that a cell can produce but most of us aren't. We want to know how many distinct genes there are because each gene will produce one kind of product or a small class of related products.<BR/><BR/>The reason for adding "functional product" to the definition of a gene is <B>not</B> to quibble about whether genes produce protein (or RNA) variants. It's to eliminate the case where a stretch of DNA is transcribed but no functional product is made (e.g., pseudogenes).<BR/> <BR/><I>Many human transcripts produce multiple functional protein products because of alternate splicing. If 'a functional product' mean ONLY ONE functional product, then many of what we consider huuman genes don't meet this criterion. If it means AT LEAST ONE functional product, then the definition fails to capture the point of the question.</I><BR/><BR/>We've known about alternative splicing for 35 years and it's never been thought to threaten our understanding of what a gene is. The point about the definition is that a gene is a region of DNA that is transcribed and not that it can only produce one particular product.<BR/><BR/>So, the point of the question is not whether proteins can be modified post-translationally or whether mRNA precursors can be alternatively spliced. The point is to decide how many fundamental genetic units are present in the genome.<BR/><BR/>Now, as it turns out, many people were unhappy that we had only a few more genes than a fruit fly so they went looking for a way to explain the embarrassment. They needed to find some rationalization to put us back at the top of the complexity heap.<BR/><BR/>The one they came up with was alternative splicing. They claimed that humans were very special because they had evolved a way of making many different proteins from each of their genes. <BR/><BR/>This rationalization had the additional advantage of accounting for the anomalous EST data that showed far too much of the genome being transcribed.<BR/><BR/>Well, unfortunately for the human centrists, the explanation hasn't worked out. The EST data is mostly artifact and it's just not true that human genes are more likely to produce multiple splice variants than the genes of other species.<BR/><BR/>Only a minor percentage of human genes produce distinct protein products by alternative splicing. The argument was never very logical anyway since the artifactual EST data of other species showed the same (pseudo)phenomonen of alternative splicing so we couldn't argue that alternative splicing was what made us special.Larry Moranhttps://www.blogger.com/profile/05756598746605455848noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-15283671148496083352007-03-24T14:43:00.000-04:002007-03-24T14:43:00.000-04:00That definition is probably satisfactory for first...That definition is probably satisfactory for first-year university biology courses, but I don't think it's very satisfactory when applied to the question of how many human genes there are.<BR/><BR/>The question of 'how many human genes there are' arises because we want to know how many distinct gene products are needed to specify humans, not how many distinct transcripts our DNA produces.<BR/><BR/>Many human transcripts produce multiple functional protein products because of alternate splicing. If 'a functional product' mean ONLY ONE functional product, then many of what we consider huuman genes don't meet this criterion. If it means AT LEAST ONE functional product, then the definition fails to capture the point of the question.Rosie Redfieldhttps://www.blogger.com/profile/06807912674127645263noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-82510731776534033632007-03-24T08:34:00.000-04:002007-03-24T08:34:00.000-04:00Yes, it's a DNA sequence that's transcribed to pro...Yes, it's a DNA sequence that's transcribed to produce a functional product [see <A HREF="http://sandwalk.blogspot.com/2007/01/what-is-gene.html" REL="nofollow">What Is a Gene?</A>].Larry Moranhttps://www.blogger.com/profile/05756598746605455848noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-60841892104254226932007-03-23T21:22:00.000-04:002007-03-23T21:22:00.000-04:00Do we have a satisfactory definition of 'gene'?Do we have a satisfactory definition of 'gene'?Rosie Redfieldhttps://www.blogger.com/profile/06807912674127645263noreply@blogger.com