Why do we yawn?

New research into the biological basis of yawning will be published soon in the journal Animal Behaviour (news summary can be found here). Researchers at Binghamton University used a species of parakeet as a model organism, since they have relatively large brains, and do not exhibit contagious yawning, as has been seen in humans and other animals.

In their study, they subjected the birds to three different temperature conditions: Warm, normal (control) and slowly increasing. They found that only the third condition had a significant effect on yawning frequency. Their conclusion is that yawning functions as a brain-cooling mechanism, much like a cooling fan on a laptop. When the environment is cooler than the body/brain temperature, taking air in quickly will function to cool the facial blood, which in turn will cool the brain. This leads to an increase in arousal, so those early morning yawns may function similar to a cup of coffee in providing a jolt of energy.

This explains the most common occurrences of yawning. Exhaustion and sleep-deprivation have been shown to increase brain temperature, so yawning in these states would make sense. In addition, yawning may be able to be used as signs of brain cooling problems, which occur in diseases such as multiple sclerosis.

The authors also point out that yawning should no longer be viewed as a sign of boredom, but as an indication of attentiveness. I will try to remember that during my next PowerPoint lecture.

Chapter 19 PowerPoint

As usual, I will be online moderating comments til 10.00 or so tonight.

Chapter 16 review packet answers

Here are the answers to the answers to chapter 16 review packet. If you need more explanation for any of the answers, leave a comment and I will respond.

Interactive question 16.5
a. helicase.....................................................h. DNA polymerase
b. Single-strand binding potein.................i. RNA primer
c. DNA polymerase.....................................j. primase
d. leading strand.........................................k. replication fork
e. lagging strand......................................l. 3' end of parental strand
f. ligase..............................................m. 5' end of parental strand
g. Okazaki fragments

Multiple choice
1. c....................................12. d
2. a...................................13. e
3. b.................................. 14. a
4. a...................................15. d
5. b...................................16. e
6. a...................................17. c
7. b...................................18. d
8. e...................................19. e
9. e...................................20. c
10. a.................................21. a
11. e

Animations

Here are the links for the DNA replication and the transcription/translation animations. I had some problems getting the Flash movies to load using Firefox, but found that IE worked fine.

As a quick aside, please be careful when you use internet resources to study. Be sure that the information you are getting is from a reputable source. A student in block 1 today had some questions about the "5-inch cap" on mRNA, and what it meant that rRNA "forms a gibbet." The student stated that the information came from a website. Upon Googling, I found the site, and the entry on RNA types. I scanned a few of the other posts, and found that grammer is a bigger issue than getting facts wrong. However, the info about RNA is pretty bad.

There is a 5' (five prime) cap added to mRNA molecules. The problem may have come from misreading the prime symbol (') as the symbol for inches, as in I am 5'10" tall. However, the symbol for inch is ", not '. And if the cap were 5 inches long, assuming that each nucleotide is 3.4 Angstroms apart, there would be approximately 370,000,000 nucleotides in the cap. Seems a little much, cosidering the whole human genome is only 3,000,000,000 base pairs.

As far as the gibbet....I have no idea where that came from.

So please be midful of this when searching for help online.