Science Friday: Why Are You So Damned Smart?

May 11, 2012

Greetings to all of you. Today I am initiating a new topic for my blog, titled Science Friday. Each Friday, I will pick a new scientific topic or experimental result and introduce it with a link to more information.

Today, I am starting with an article about partial cell DNA duplication and the role it may have played in developing Homo sapiens sapiens.

Yes, I know this is not about law and this is a law blog. Well, guess what? Even lawyers need to know some science and besides, it is interesting for its own sake.

First, a little background.

The nucleus of each cell in our bodies contains a complete copy of the human DNA genome. Prior to dividing to create a new cell, each cell creates another complete copy of the human genome. Mistakes happen occasionally during this process and the error becomes a genetic mutation, if the cell does not correct it.

Mutations are not inherently good or bad. Whether they are good, bad or neutral depends on the environment in which the organism exists. Most of the time they are neutral. Sometimes, however, a mutation creates a competitive advantage or disadvantage for an organism that allows it to prosper or struggle in the existing environment relative to other organisms that belong to the same species. Depending on the environment, successive generations that inherit the advantage may expand in number and end up prevailing over organisms that inherit the disadvantage and gradually die out. Sometimes the environment changes radically and suddenly amplifying the importance of the advantage or disadvantage. We call this process natural selection.

Duplication is one type of error that occurs during genome replication. When that happens, a section of the genome is copied twice instead of just once. The extra copy can change over time gaining mutations or losing parts.

In a paper published today in the peer reviewed scientific journal, Cell, genetic researchers have reported that they have discovered that the human gene SRGAP2 has duplicated itself twice, approximately 3.5 and 2.5 million years ago. This corresponds to the period when the brains of our ancestors began to expand, increasing cognitive ability, and the now extinct hominin Australopithecus declined and disappeared in favor of the genus Homo that led to us, Homo sapiens sapiens.

The more recent duplication was an incomplete duplication. Using mouse DNA in the lab, they replicated the incomplete duplication and discovered that it appeared to speed the migration of brain cells during development making brain organization more efficient.

To read more about this study, go here to read an article in Discovery News by Jennifer Welch, reporting for LiveScience.com on Sunday, May 6th.


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