Women are born with two X chromosomes, one inherited from their mother and one inherited from their father. However, to ensure the balance of gene expression, every cell in a woman's body randomly inherits one X chromosome, while the other is either shut down or inactivated. In theory, the X chromosome either comes from the father or the mother, and this randomness should be fair. However, in reality, there are intense "expression rights tug of war" behind it, and the outcome may affect a person's life. In fact, there is a common and unfair phenomenon in human genetics: in some cases, the X chromosome in some women's bodies tends to be inherited from either parent. This phenomenon is called "X chromosome inactivation shift". For example, the color of a female cat's fur, whether it appears orange or black, is controlled by two X chromosomes. If a cat's cells are more inclined towards the maternal X chromosome that controls orange color, then the cat's fur color will be more orange. However, this' maternal love bonus' may not necessarily be a good thing in brain cells. It may become the "mastermind behind" cognitive impairment and accelerated aging. In order to explore this mysterious phenomenon, scientists at the University of California, San Francisco have bred several female mice, some of which only express the X chromosome from the mother's body, while others express both the X chromosome from the mother's body and the father's body. As a result, only female mice with active maternal X chromosomes have poorer memory and learning abilities as they age. In their brains, the maternal X chromosome accelerates the biological aging of the hippocampus, a crucial brain region for learning and memory. Scientists subsequently determined that certain genes were completely 'disabled' on the maternal X chromosome of female mice, while not on the paternal X chromosome. Are these genes related to cognitive impairment? So, scientists used CRISPR gene editing technology to activate these inactive genes. Something magical happened: the intelligence level of elderly mice improved to a certain extent. This may mean that whether the X chromosome source of brain cells is from the mother or father may have an impact on brain health. When a woman's brain cells rely solely on the X chromosome inherited from her mother rather than her father, the aging rate will be faster. These findings help explain the differences in brain aging, cognition, memory, or risk of developing brain diseases between genders.