Last Resort

Mitotic Crossover

If you remember your basic high school biology course (or not, as the case may be), you may recall the cell division topics mitosis and meiosis. (Mitosis=growth, regeneration, etc. Meiosis=germ cells, reproduction, gametes)

You may remember that in meiosis a process called crossover occurs, in which DNA is exchanged between homologues, or the genetic codes from the organism's parents. This is one of the reasons why we cannot end up with identical siblings (unless, of course, they are twins). 

You may not have known that crossing over occurs in mitosis as well. However, it is not measurable, because sister (identical) chromosomes look the same whether or not they have crossed over. 

However, in rare cases, a mistake can occur, leading to genetic abnormalities such as recessive trait spotting (like a patch of red hair on a black haired individual) or even cancer. 

For more information, check out: http://www.ncbi.nlm.nih.gov/books/NBK21438/

Anti-terrorism...one vaccine at a time

http://www.nytimes.com/2011/07/12/world/asia/12dna.html

Genetics-Define Life

I sat in a class of sophomore students today trying to come up with the definition of life. Instead of a definition, we found a series of possible criteria to judge whether something was indeed living. I was quite surprised by the realization that there is a lot of controversy over what the definition of life is. I remember in my biology class we said something had life as long as it was actively undergoing cellular processes. However, in Dr. V's class at Tulane, she refers to a living thing as having the following qualities:

1.Cells and organization

2.Energy use and metabolism

3.Response to environmental changes

4.Regulation and homeostasis

5.Growth and development

6.Reproduction

7.Biological evolution

Food for thought.

Cations and Anions

Cations and Anions are concepts in chemistry. They are ions with a positive or negative charge. You can tell which is which in a few easy ways.

Cations - the t looks a little like a cross, or a plus sign! + cations are positive.

Anions - the common prefix "a" often stands for "without" or "against". Think of it as against a charge. -

Plural Octopus

I learned recently that I have been saying the plural of octopus incorrectly for many years. Apparently the word octopus originated from the Greek oktṓpous. The correct plural of this is octopodes; many incorrectly assume that the word is Latin, which would result in a plural of octopi. Currently most people accept octopi or octopuses as reasonable, especially as octopodes are rarely encountered, as the octopus is a mostly solitary creature. 

Image from: XKCD

Blood Letting

Blood letting has been a commonplace practice for thousands of years (all the way back to the Ancient Romans). It is estimated to have been the cause of at least hundreds of deaths (including, some say, that of America's first president, George Washington). But did you ever wonder where the idea came from?

First, a little background in genetics. Men have an X chromosome and a Y chromosome. Women have two X's. The fact that men only have one X makes them more susceptible to certain genetic diseases.

This fact was not unnoticed in Ancient Greek and Rome. Some physicians looked at the fact that women were not so susceptible to particular diseases (such as epilepsy). They then looked at what women had that men did not. What caught their attention was the menstrual cycle. They connected the loss of blood to the immunity to certain diseases.

Galen, a very influential Roman doctor, loved to write about the wonders of bloodletting as a treatment to disease. Already a common practice, his book renewed popularity of the treatment, and bloodletting was then continued for hundreds of years.