How do mutations lead to genetic variation?

Mutation can be defined as the change in the sequence of DNA. This can be cause to several factors such as physical or chemical mutagens.

Mutation can lead to the create entirely new allele in a population. Random fertilization or recombination that takes place between homologous chromosomes during the process known as meiosis also leads to mutation.

This is how mutations can lead to genetic variation.

             Genetic variation is based on three primary sources.
1. Mutation
2. Gene flow
3. Sexual reproduction.
Mutation is the change in DNA sequence. Single mutation has effect, but many mutations are responsible for genetic variation. Sickle cell anemia is an example of mutation. 

Explanation:

Cell transport refers to the movement of substances across the cell membrane. Probably the most important feature of a cell's phospholipid membranes is that they are selectively permeable. A membrane that is selectively permeable, or semipermeable, has control over what molecules or ions can enter or leave the cell, as shown in Figure below. This feature allows a cell to control the transport of materials, as dictated by the cell's function. The permeability of a membrane is dependent on the organization and characteristics of the membrane lipids and proteins. In this way, cell membranes help maintain a state of homeostasis within cells (and tissues, organs, and organ systems) so that an organism can stay alive and healthy.