Tweezers for chromosomes
Chromosomal rearrangements were diagnosed using laser tweezers
Mikhail Orlov, Naked Science
The human genome consists of 23 pairs of chromosomes, one of which is sexual, identical in the case of women (XX) and unlike in the case of men (XY). This whole set includes structures of different sizes, having a constriction and so-called shoulders, which sometimes differ markedly in size.
Sometimes quite serious changes occur in such a set. For example, individual chromosomes in a pair may be doubled (as in the case of Down syndrome) or fall out (an example is the Shereshevsky—Turner syndrome, when only one X chromosome remains of the genitals). Smaller-scale rearrangements are also described: for example, in syndromes Aldred and Wolf —Hirshhorn disappears a small section of the chromosome. In other cases, a part of the chromosome may double or turn 180 degrees.
About one percent of people live with chromosomal aberrations of one kind or another. Moreover, they are considered the most common cause of spontaneous termination of pregnancy in the early stages. Therefore, it is very important to have reliable and fast diagnostic methods that allow detecting such mutations in time. Sometimes doctors who suspect another case of chromosomal rearrangements cannot understand which one they are dealing with, or estimate the size of the defect — all this makes it difficult to predict the course of the disease.
To solve such problems, researchers from the University of Copenhagen (Denmark) have proposed diagnostics based on high-precision biophysical methods. It made it possible to achieve very high efficiency and notice those chromosomal aberrations that are indistinguishable using standard methods.
"Ideally, we would like to take a sample from a person, for example, with infertility and use our method to analyze the chromosomes, detecting the defects present. In principle, it can also be useful for the study of other chromosomal rearrangements and diseases, in particular cancer," said Professor Ian Hickson from the Department of Cellular and Molecular Medicine, one of the authors of a new article in Nature (Meijering et al., Nonlinear mechanics of human mitotic chromosomes).
The scientist notes that modern hospitals (for example, in Denmark) chromosomal aberrations are already being diagnosed, but their technologies are far from perfect. "Now, when studying chromosomes, they are exposed to chemical reagents with which they are fixed. All this is reminiscent of a veterinarian who wants to examine a pet dog, but for this he must first make a stuffed animal out of it," explained Hixon.
The solution proposed by the Danes is much more delicate and high-tech. They use laser or optical tweezers — a special tool that allows you to manipulate microscopic objects and even individual molecules. Scientists use optical tweezers in protein research and for particularly accurate measurements.
When working with chromosomes, this technique, in fact, works like a microscope with very high resolution. Moreover, in this case it is possible to move, squeeze and stretch chromosomes. For example, with such manipulations, a piece at the end of the chromosome may fall off, which indicates certain mutations. It turns out that with the help of optical tweezers it is possible to notice even the smallest defects and carry out better diagnostics.
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