Because the black and orange colors are determined by joining two separate pairs of X-chromosomes, calicos are nearly always female, except in the event of an extra Y mutation on one of the pairs.
One would hardly expect calico cats to hold the key for treating and preventing obesity in humans, known for sleeping all day and being spoiled by their owners, but their unusual black and orange color patterned coat may hold the secret. Because the black and orange colors are determined by joining two separate pairs of X-chromosomes, calicos are nearly always female, except in the event of an extra Y mutation on one of the pairs. The way the genes interact is what is most intriguing to biologists. In order to produce the pattern, both sex-linked X-chromosomes come together, pushing out other traits. In order for them to join together, one X-chromosome is silenced in the pairing of cells. The consequence is that the genes produce one phenotype over the other, preventing one color from dominating, for example. This determination results in a compromise of both.
Now, using a new technology called soft X-ray tomography which allows for three-dimensional views of cellular components, researcher Elizabeth Smith from the University of California- San Francisco is able to spot the activity of chromosomes and discovered that obesity is also determined by a similar interaction among X-chromosomes.
With this sort of magnification, researchers like Smith are able to probe specific genes within the cell’s infinitely small nucleus, delving deep into live, hydrated microscopic cells for the first time. Although scientists have known for ages the size and structure of nucleotides, this technology has now enabled them to observe and isolate the specific parts. This time their focus was on the inactive cells, the behaviors of genes that have been switched off and how they affect the system of the living animal, specifically marking them with fluorescent probes, and even recognizing the isolated parts that make up a single chromosome.
Using the latest in gene therapy techniques, Smith and her colleagues may in the future be able to regulate the shuffling of DNA chromosomes without significantly harming the DNA or the neutrality of the mutations the genes produce.