Mutations in the DNA sequence of a gene affect the expression of the gene or the sequence of amino acids in an encoded protein --may or may not
--will always
--will not affect the expression of the gene, but will change the sequence of amino acids in the encoded protein
--will never

In an experiment examining the effects tai chi on arthritis pain, callahan (2010) selected a large sample of individuals with doctor-diagnosed arthritis. half of the participants immediately began a tai chi course and the other half (the control group) waited 8 weeks before beginning. at the end of 8 weeks, the individuals who had experienced tai chi had less arthritis pain that those who had not participated in the course.