What are the steps (in the correct order) that link a change in the base sequence of a gene to a change in the phenotype of an organism like a mouse or a human? see section 16.2 (page 339) ?

The answer is DNA to RNA to protein. The change in DNA sequence will be reflected (through complementary base pairing) on the formed Messenger RNA during transcription. Subsequently, during translation of the mRNA to protein (by ribosomes), the amino acid sequence will change due to changes in the codons. Proteins, as you may know, are what determines the phenotype of organisms while DNA determines the genotype of the same organism.

osteogenesis imperfecta (oi) refers to a congenital ailment of bones. in the condition, the bones become brittle or fragile. this ailment is a general result of the defect or mutations in the genes (colia1 or colia2). this mutation results in imperfect collagen formation either in quantity or quality wise.  

there are eight kinds of oi defects, and each kind varies with certain distinctions in symptoms. the usual symptoms include frequent bone fractures, loss of hearing in infants, protruding eyes, discoloration of the white in the eyes, respiratory issues, loosening of the joints, short stature, and other symptoms.