The human somatic cell contains 23 pairs of chromosomes (46 chromosomes) that carry the genetic material. These pairs are divided into 22 pairs of autosomal chromosomes (which are responsible for determining physical traits and traits), and one pair of sex chromosomes (which is responsible for determining human sex).
Each chromosome consists of a single DNA molecule and a variety of proteins that perform multiple functions. Read also For the first time, scientists have captured a stunning video of the RNA folding mechanism For the first time, scientists have captured a video of the twisting of DNA molecules Scientific breakthrough and multiple applications.. catching DNA from the air became possible ممكن Not what it looks like in science books.. 3D imaging of human chromosomes for the first time
Chromosomes can be seen using a light microscope during the stage of cell division known as the metaphase, in which the chromosomes line up at the cell’s equator. These chromosomes appear in the form of the letter “X” (X), and carry the genetic information of the organism, and are passed on from parents to children.
These 46 chromosomes are classified and arranged according to their size and shape in a process known as karyotyping, and this process is of particular importance to geneticists and doctors alike, as they can identify the presence of any structural defect in the construction of chromosomes, or any Numerical or genetic abnormalities that may result in genetic diseases; Hence, it can be used to diagnose these diseases early.
Therefore, it is important to know the mass occupied by these chromosomes within the nucleus. Although some methods that study DNA sequences can inaccurately determine the mass of DNA during the tropics, the weight of the chromosomes that host these components has remained a mystery. This is due, in part, to the fact that we do not yet know the mass occupied by the protein component of these chromosomes.
A new approach offers the answer
This question was the focus of a new study conducted by scientists at University College London in the United Kingdom, using one of the most powerful X-ray beams produced by the spin-synchronous particle accelerator known as the Diamond Light Source. The were published results of the study in Journal of “Chromosome Research” on March 31.
To calculate the mass of chromosomes, the scientists used a new method known as “Ptychography”, in which electrons are passed through these chromosomes to produce a three-dimensional model of them.
By calculating the exact number of electrons recorded for each chromosome, the scientists were able to estimate the mass of each individual chromosome, and then estimate the mass of the total chromosomes. The measured individual mass of each chromosome also helped to estimate the mass of the protein component and the mass of its nucleic acid separately.
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According to the press release published by University College London, the results of the study indicated that human chromosomes weigh 20 times greater mass than the DNA inside them, which is a much greater mass than researchers previously expected.
In this regard, says Ian Robinson, the study’s senior researcher and professor of physics at the same university, “The 46 chromosomes in our cells weigh 242 pg” (a picogram is one trillionth of a gram).
“This weight is heavier than we expected,” Robinson adds. “So its doubling (during the process of cell division) indicates an unexplained increase in the mass of these chromosomes.”
Although this study provides a unique estimate of the mass of chromosomes for the first time, scientists do not have any good explanation for the reason for the presence of this extra mass.