The Gay Gene Debate

A heated debate over the existence of a "gay gene" emerged from a 1993 report that linked DNA markers on the X chromosome to male sexual orientation.
Since then, questions arose regarding the validity of those results.
But researchers say a new study is to be taken; a study that takes a different approach. Its goal was not to replicate those findings but to search for new genetic markers associated with male sexual orientation.
"Since sexual orientation is such a complex trait, we're never going to find any one gene that determines whether someone is gay or not," says Mustanski. "It's going to be a combination of various genes acting together as well as possibly interacting with environmental influences."
Previous studies in male twins have suggested that between 40%-60% of the variability in sexual orientation is due to genes. The rest is thought to be due to environment and possibly other biologic but nongenetic causes.
In the study, researchers analyzed the genetic makeup of 456 men from 146 families with two or more gay brothers.
The genetic scans showed a clustering of the same genetic pattern among the gay men on three chromosomes -- chromosomes 7, 8, and 10. These common genetic patterns were shared by 60% of the gay men in the study. This is slightly more than the 50% expected by chance alone.
The regions on chromosome 7 and 8 were associated with male sexual orientation regardless of whether the man got them from his mother or father. The regions on chromosome 10 were only associated with male sexual orientation if they were inherited from the mother.
Researchers say the next step is to verify these results in a different group of men to see if the same genetic regions are associated with sexual orientation. If the findings hold up, then they could start to look for the individual genes within these regions linked to sexual orientation.
Elliot S. Gershon, MD, professor of psychiatry and human genetics at the University of Chicago, says the study represents an important step forward in understanding how genes affect human sexual orientation.
"It is worth testing genes within a region of linkage to see if one of them has a variant that is more frequent in men who are gay than in men who are not," says Gershon. "There is an argument that has been made in public press that it doesn't make sense to study conditions or traits that are behavioral. But this suggests that there is a genetic contribution to this particular trait of same sex orientation."

Black Death casts a genetic shadow over England

The Black Death continues to cast a shadow across England. Although the modern English population is more cosmopolitan than ever, the plagues known as the Black Death killed so many people in the Middle Ages that, to this day, genetic diversity is lower in England than it was in the 11th century, according to a new analysis.

Rus Hoelzel at the University of Durham, UK and his colleagues looked at the mitochondrial DNA from human remains at 4th and 11th century archaeological sites in England, and compared them to samples from the modern population stored on DNA databases such as GenBank. They found there was more variation in the ancient mitochondrial DNA sequences than in modern sequences.

Hoelzel thinks random genetic drift may have lowered genetic diversity naturally. But the large unexpected drop in diversity was more likely to have been caused by population crashes following major outbreaks of the Black Death in England during the 1340s and the 1660s.

"The main factors in support of a role for plague are the timing and the fact that it affected different families [to a differing degree]," says Hoelzel. It is known that plague affected some families more than others, so their mitochondrial DNA would have been less common among survivors, Hoelzel says.

"I'm not at all surprised with the result," says Susan Scott at the University of Liverpool, UK. "We're talking about one of the worst disasters humans have faced. It destroyed about half the population of Medieval Europe in three years."
But the effects may have been most severe in northern Europe. Hoelzel and his team note that DNA sequences from modern Italians are just as variable as those from their 7th century ancestors.

According to Hoelzel, this finding may reflect migration patterns after the Black Death, rather than a less severe outbreak in southern Europe. "Throughout the recent past, there have been movements from the Middle East into southern Europe, and the Middle East population retains a great mix and diversity," he says.

Visit:

http://www.newscientist.com.ezproxy.library.uq.edu.au/article.ns?id=dn12393&feedId=online-news_rss20

Elizabeth Philipson 41770575

The World Behind The Door

DNA to RNA to proteins. Seems simple enough. If one sits to think about it however, it becomes more and more incomprehensible. How can it be that one twin, with identical genetics to their sibling, can develop schizohrenia or cancer whilst the other does not? How can it be that complex organisms, such as humans being made from only 2% of their DNA?
This is the question that researchers are setting out to solve: is it really only 2% which is used? Is the rest really just ‘junk’? Research being carried out by the University of Queensland very own John Mattick and his teams of researchers states that this is not so. A revolution in genetics is at a forefront.
Organisms are extremely complex, which requires larger and more intricate networks to control their function. It has now been suggested that this complexity, which is not encoded on the 2% of genetic material, is held within the ‘junk’ DNA.
There is now copious amounts of evidence which say that ‘junk’ DNA encodes for myriad RNA, which doesn’t code for proteins, but rather interacts with DNA of genes and messenger RNA that instruct the creation of proteins. It has been said that this myriad RNA is “a self-organising operating system that ultimately determines how, when and where genes shall work, as well as coordinating their interactions and that it is system all on its own. Dr Mattick says that the thought occurred to him when he was considering introns. Why would evolution keep these long stretches of DNA if they were not funcitonally important?
Dr. Mattick believes that this myriad RNA control some of the most simple processes, such as manipulating chromatin to be ready for gene activity, and controlling the process of methylation.
Though there is a long path of discovery to continue along, geneticists have determined, by working out some of the important mechanisms, that this ‘epigenetic’ part of the genome plays and vital role in aging, growth and cancer. Mutations of this material, known as ‘epimutations’ are now suspect to diabetes, bipolar disorder and schizophrenia.
For any real genetic modification to occur, this hidden world must be understood. Is this world the reason why some gene transfers fail? And perhaps this is the real reasoin for the individuality seen everywhere? This discovery, this new universe could tip all the knowledge about genetics present today.

“There is a whole new universe out there
that we have been blind to. It is very exciting.” Timothy H. Bestor


To read more:
http://www.biotechnews.com.au/index.php/id;119302135
http://jeb.biologists.org/cgi/content/full/210/9/i-a
http://community.emmawillard.org/science/natural-sciences/ns-classes/advanced-topics/articles/epigenetics.pdf

Anaethesia

Inducing anaesthetic drugs leads to numbness and inactivates motor axons, which makes patients unable to move the body part spontaneously. But, according to a hypothesis published in Nature, it might be possible to induce anaesthesia without dysfunctioning other sensory systems.

Capsaicin, a pungent factor in chilli pepper, and QX-314, a local anaesthetic play a key role in the novel anaethesia. The idea of this is that when both capsaicin and QX-314 are applied, capsaicin first stimulates TRPV1, and then QX-314 which usually cannot permeate into a cell membrane is allowed to enter the cell through the activated TRPV1. The QX-314 inside the cell acts in the same way as other anaethestics do. QX-314 blocks sodium ion channels. This consequently anaethetises the nerve.


The point of this is that without passing through an activated TRPV1 channel, QX-314 cannot function as anaethesia. Most importantly, TRPV1 only exists in nociceptor (pain-sensing) neurons. That is why there is a great prospect of inventing a novel anaesthesia which lets patients move freely but feel no pain.


Binshtok, AM, et al 2007, “Inhibition f nociceptors by TRPV1-mediated entry of impermeant sodium channel blockers”, Nature,
http://www.nature.com/nature/journal/v449/n7162/full/nature06191.html.

Detecting Disease Through Your Genes

Researchers led by Doctor Krassen Dimitrov at the University of Queensland have developed a new technique for mapping gene expression which could allow diseases to be diagnosed before any symptoms develop.
The technique involves mixing flourescent 'nanostrings', which bind to RNA molecules, with the subject's blood. The order of different coloured nanostrings can tell researchers which gene they are looking at. The different genes are then counted and inventoried digitally, giving a clear picture of gene expression in the subject. This will give a good idea of what the body is doing when the test is done. It is much more accurate than older teqniques such as DNA microarrays, which use a less clear analogue measuring system.
According the Doctor Dimitrov, this technique could be used to predict and prevent disease before any symptoms appear.

Why Some Crave Sugar More Than Others!

There is no one favorite food in this world. They vary from individual to individual, depending on personal taste and preference. It is believed the factors which influence this characteristic are related to environment as well as genetics. Past food studies have discovered that sweet tasting foods which are high in sugar seem to be the most popular food category among people. However, have you ever wondered why some people crave sugary goods more than others? The craving for foods high in sugar vary from person to person, but the underlying reasons why are still unclear. To better understand this concept, research teams examined the effect of a common variation in a gene that controls the entry of sugar (glucose) into cells. The gene is called glucose transporter type 2 or GLUT2.

The researchers composed an experiment to test the effects of the genetic variation in two distinct populations. One population consisted of older adults who were all either overweight or obese. The other population consisted of generally healthy young adults who were mostly lean.

The diet of the participants in the first population was assessed by recording all of the foods and beverages consumed over a three day period, and repeating this 3-day food record two weeks later to ensure that the effect was reproducible. All participants were interviewed face-to-face during the two visits to the research centers. For the second population, the study participants used a questionnaire that asked about the foods and beverages typically consumed during a one month period.

Blood was drawn from each participant, and their DNA extracted. The researchers examined the genotype distribution and compared the food intake data each participant provided between individuals with the variation and those without the variation in GLUT2. The DNA samples that carried the variation in GLUT2 were associated with consuming more sugars in both populations studied.

Hence, it was found that a variation in the GLUT2 gene is associated with a higher intake of sugars among different populations. These findings may help explain some of the individual variations in people's preference for sugary foods. It's especially important given the soaring rates of obesity and diabetes throughout much of the world.

Full article:
http://www.sciencedaily.com/releases/2008/05/080514064928.htm
Image from: http://thenrb.files.wordpress.com/2007/09/donuts.jpg

- Sarah Chan (41768778)