The Difference Between a Chromosome Abnormality and a Single Gene Defect

What is the difference between a chromosome abnormality and a single gene defect?
There are approximately 70,000 genes contained on the 46 chromosomes in each cell of our body. This means that one chromosome contains thousands of genes. A person can have normal chromosomes in number and structure, but still have a disease or condition caused by a mutation in one or more of the genes on the chromosomes. A single gene defect usually does not cause the chromosome structure or number to be abnormal.

Similarly, a person can have normal genes, but, because they have extra copies of genes due to a chromosome abnormality, the extra copies can cause the genes to not work properly.

This is an important distinction to make. Consult your physician or genetic counselor for more information.

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