A human embryo contains 46 chromosomes organized into 23 pairs: 22 pairs of non-sex chromosomes, called autosomes, and one pair of sex chromosomes (XX in a female and XY in a male). One chromosome in each pair is inherited from the mother and one from the father.
Located along these chromosomes are approximagely 25,000 genes that carry instructions for making proteins. Through the proteins they encode, your genes determine how your body develops and functions.
What is a gene mutation?
A gene mutation is a permanent alteration in a gene. Disease results from the altered gene's inability to produce a protein the body needs for normal functioning. The diseases produced by gene mutations can be mild, severely debilitating, or fatal.