Chapter 12.3, Problem 1CSC

Muscles, Mutations, and Myostatin

The sequence of nucleotides in a gene determines the function of the protein that it encodes. The myostatin gene of Herefords and most other breeds of cattle has a nucleotide sequence that differs from the sequence in the Belgian Blue myostatin gene. The Hereford gene codes for a protein that limits muscle size; the Belgian Blue gene, however, codes for a completely nonfunctional myostatin protein, so their muscles become oversized. Both Hereford and Belgian Blue cattle breed true—their offspring have the same nucleotide sequence in their myostatin genes as their parents do, which occurs because DNA replication, from cell to cell and from parent to offspring, almost always produces exactly the same nucleotide sequences, time after time. How do cells replicate their DNA so precisely?