I have a genetics question: is it true that we're not necessarily 25 percent of each grandparent in terms of dna? if not, then how much?

Mitochondrial DNA: We inherit about 25% DNA from each grand parent. All of the mitochondrial DNA comes from the mother, and her mother. Mother contributes more DNA to a male child as X chromosome is larger than Y chromosome. I do not see a practical point to this technicality. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex.