When limiting factors increase, diversity in populations decreases. In this sense "limiting factors" can be anything from a lack of resources to a lack of food, meaning it's harder for the population to survive.
Duchenne muyscular dystrophy is caused by a mutation on the X chromosome, so a male gets it from his mother's X, if she is a carrier. The male child gets a Y and no X from his father, so the disease is always transmitted through the X from the mother. If a female gets Duchenne muscular dystrophy she has to have two X chromosomes, one from a carrier mother and another from from an affected father. This is virtually impossible because most males die before childbearing age and there is no way a female child can get an X from a man who does not live long enough to procreate. About eight percent of carrier women do show some muscle weakness, but they do not have the disease.
<span>A solution is hypertonic to a cell if it has a higher solute (dissolved substance) concentration than the cell does. As a result, it also has a lower concentration of water than the cell does. Cell membranes and plant cell walls are semipermeable barriers, which means that certain molecules can diffuse through them, while other molecules can not.</span>
