Journal/Blog

WHY DO MEN HAVE NIPPLES?

           I would like to explore another vestigial structure, the male nipple. You may think this is a redundant post after the investigation of the appendix, but there are some important evolutionary differences.

            The common thread of a species is its genome. The human genome is what makes us all so similar (and yes, we are similar). The single largest cause of difference in our species is the presence of the Y chromosome. Due to the X and Y chromosomes, men and women have distinctive morphological and hormonal features. The sexual organs, for example, are a direct cause of these genes and known as a sexual dimorphism. Traits that are advantageous to one sex and harmful to the other, like testosterone, are isolated to the genes of the X and Y chromosomes. This sexual genetic isolation is called uncoupling. Nipples, it is suspected, have not “uncoupled” to become a strict female trait because they are not a genetic disadvantage to males. To solidify this reasoning, let us consider a hypothetical idea: if men had large breasts as well, perhaps they would have been at a disadvantage for hunting. This disadvantage would have caused starvation, or at least less food to attract a partner. Evolution would slowly wean out those with large breast, and the trait would have to become ‘uncoupled’ to allow for a sexual distinction. Breast, then, would only be expressed in the presence of two X chromosomes. I guess the motto of the male nipple is “no harm, no foul”.

http://www.scientificamerican.com/article.cfm?id=why-do-men-have-nipples

Simon Shave

How did we get mitochondrial DNA?

posted Feb 23, 2012, 8:31 AM by Jenn Burt

We talked about this briefly, but we did not really dive into this area in detail. In case some of you are still confused, here is a reasonable link discussing the theory of endosymbiosis. The theory was most advanced by a scientist named Lynn Margulis who published a paper in 1967 calledThe Origin of Mitosing Eukaryotic Cells. For those of you who are more keen, here is a link to a very comprehensive paper detailing the origin and evolution of eukaryotes and the advances being made in mitochondrial research.

Genetic drift

posted Feb 22, 2012, 11:21 PM by Jenn Burt   [ updated Feb 22, 2012, 11:22 PM ]

If you recall, we discussed in class the other day the various other processes that can influence the process of natural selection within and among populations. The items we discussed were genetic drift, gene flow, and population bottlenecks. Here is the link to the animation I showed you to illustrate gene drift:

Sequencing DNA

posted Feb 22, 2012, 11:03 PM by Jenn Burt

In Monday's class we went over the procedure that is commonly used to sequence unknown regions of DNA. Here are the animations I suggested you look at. They show the chain termination method, otherwise known as the Sanger sequencing method.




From land back to sea - cetacean evolution

posted Feb 20, 2012, 3:13 PM by Jenn Burt

How did cetaceans evolve? It surprised some people in class to see that whales descended from ancestors that walked the earth. Can somebody give a quick summary of this evolutionary story?

Is the appendix still evolving?

posted Feb 20, 2012, 3:09 PM by Jenn Burt

This question came up in class today. We discussed that the appendix is a vestigial structure - a remnant of our ancestral history - but what is happening with it in today's generations? Are we seeing people born without appendices? Will we eventually 'lose' our appendix in future generations? Does the appendix have a function that it provides therefore suggesting we might not ever 'lose' it?

Stem cell policy in Canada

posted Feb 18, 2012, 12:58 PM by Jenn Burt   [ updated Feb 18, 2012, 1:00 PM ]

After our engaging debate on Friday, I thought I would post some information on the stem cell research policies in Canada. The guidelines and policies for stem cell research (and many other health sciences research) is determined by the Canadian Institutes for Health Research (C.I.H.R). On their website, they have all the most current guidelines and policies. You can just browse through (link here to the page shown below).

Also available from this site is a PDF document that is a discussion about research and ethics in relation to stem cell research in Canada. It has a good background and details on our policies and ethical guidelines. Link to document here. I couldn't find a date on the document, so I don't know when it was published.

Finally, here is another good paper that discusses the background to stem cell related policy in Canada and the laws and guidelines that govern research. It's worth a browse through - link here.

Stem cell art

posted Feb 15, 2012, 9:31 PM by Jenn Burt   [ updated Feb 15, 2012, 9:31 PM ]

Check out this exhibit that was at the Glenbow Museam in Calgary in spring of 2011 - an exhibit totally devoted to stem cell inspired art. Click here.


Stem cell videos

posted Feb 15, 2012, 1:57 PM by Jenn Burt   [ updated Feb 15, 2012, 2:36 PM ]

Here is the video from lecture 2 on stem cells:

Here's the website that shows embryonic development in a human versus a dish of ES cells.

Here's an illustration of the FACS analysis we talked about in class:
I'm sorry, I can't actually find the source that I got this from at this moment.



Neural stem cells and memory?

posted Feb 15, 2012, 8:48 AM by Jenn Burt   [ updated Feb 15, 2012, 1:35 PM ]

What is known about the ability of neural stem cels to regenerate memory? Are there any studies out there exploring this possibility?

In February 2010, a study entitled "Allopregnanolone reverses neurogenic and cognitive deficits in mouse model of Alzheimer's disease" was published. Researchers were studying the effects of Allopregnanolone (APa), a naturally occuring steroid from the central nervous system, on the memory and learning function of a 3 month old mouse with Alzheimers. They found that when APa was injected into the mouse, it restored its memory performance to that of a normal 3-month old mouse. They concluded that APa could potentially be used as a regenerative therapeutic for cognitive defects and to restore memory in patients with conditions such as Alzheimers disease. - Kelly McQuade

Can we create immortality?

posted Feb 15, 2012, 8:47 AM by Jenn Burt   [ updated Feb 15, 2012, 8:48 AM ]

Great question from class yesterday: Could we induce a mutation so that telomerase was left "turned on" which would cause "immortality"? (Hint, see Ridley Ch.14 for possible answers)

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