![]() This process occurs at a very early stage of embryonic development in female placental mammals, including elephants, wolves, humans, and cats. Now, let's delve into how this mechanism works.įor reasons not yet fully understood by biologists, one of the two X chromosomes in each cell of the female body begins to randomly produce RNA molecules called Xist. Today, it is known as X chromosome inactivation or Lyonization, named after Mary Lyon in recognition of her contribution. Subsequent studies conducted over the years have provided growing evidence for the existence of this mechanism. This mechanism prevents the genes on the silenced X chromosome from producing proteins, effectively addressing the issue at hand. In 1961, researcher Mary Lyon proposed the existence of a mechanism that randomly silences one of the X chromosomes in the cells of females. To achieve this balance, females have a mechanism that allows only one X chromosome’s genes to be active and produce proteins. ![]() Such a mechanism needs to ensure that the total amount of proteins produced according to the instructions encoded in those genes, remains consistent in both males and females. Therefore, a mechanism is necessary to balance the expression of genes originating from the X chromosome. The X chromosome contains numerous genes associated with the immune system, and having two X chromosomes increases the susceptibility of women to develop autoimmune diseases such as lupus. In fact, the presence of an additional X chromosome in females can create problematic situations. Having two X chromosomes is not essential to living a normal life, as evident from the composition of sex chromosomes. Microscopic image of a male’s chromosome pairs, with the sex chromosomes positioned at the bottom right | CNRI, Science Photo Library The Silent X In all mammals, females have a pair of X chromosomes, while males possess one X chromosome and one Y chromosome. In rare cases, individuals can be born with other chromosome combinations, such as XXY, XYY, or only a single X without a Y chromosome. In contrast, males have only one X chromosome, and a much shorter chromosome called the Y chromosome. In all mammals, females possess two similar sex chromosomes, called X chromosomes. The remaining is referred to as the sex chromosomes. Out of the 23 pairs of chromosomes in humans, 22 pairs consist of two chromosomes that are similar in size and contain similar types of genes, both in males (boys and men) and in females (girls and women). In other words, each of us inherits 23 chromosomes from our mother and 23 chromosomes from our father, resulting in a total of 46 chromosomes in most of our cell’s nuclei. Each of those pairs consists of one chromosome inherited from our mother and one chromosome inherited from our father. Human DNA is divided into 23 pairs of chromosomes. Regarding Boys and GirlsĬhromosomes serve as the structures that house our genetic material, DNA, packaged within the cell nucleus. Surprisingly, cats, or more precisely, female cats, can teach us an important lesson about a genetic phenomenon that also occurs in humans, known as X chromosome inactivation. However, we seldom associate cates with lessons in genetics. When someone says "cats", our minds typically conjure images of their cuteness, fur and playful nature, or we may recall amusing viral cat videos that made us laugh.
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