HPCGG: Lab for Molecular Medicine

Harvard Medical School - Partners Healthcare Center for Genetics and Genomics

Basic Genetics

When someone says that a disease is "genetic" this means that there is a change in a gene.
But what is a gene? How can a change in a gene cause disease?

Our bodies are made of trillions of different cells. Cells make up all our tissues (hair, teeth, nails, muscles, blood, bones, etc.).


Almost every cell has a nucleus. Each nucleus contains genetics material (called DNA). DNA is unique material that makes us different from each other.

In every nucleus of every cell, the DNA is divided into a set of thread-like structures, called chromosomes. Every nucleus has 23 pairs of chromosomes. The first 22 pairs are numbered 1-22 and the 23rd pair is our gender chromosomes. They determine if we will be male (XY) or female (XX).

Mother Father Pair of Chromosomes	For every pair, one chromosome is from the mother and one is from the father. This means that half of our unique genetic material comes from each parent.
Chromosome	Every chromosome contains many genes. Together, our genes are like an "instruction manual." They tell our bodies how to run properly. For example, there are hundreds of genes that tell our hearts how to function.
Chromosome	Sometimes a change (or error) can occur in a gene. A change in a gene is called a mutation. A mutation is like a misspelled word in the "instruction manual". It can cause the gene to stop working properly. This can lead to disease.

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