To review briefly, chromosomes are packages of genetic information that we inherit from our parents. Chromosomes carry the instructions (genes) for our growth and development. Typically, each individual has 46 chromosomes that come in 23 pairs. One chromosome in each pair comes from the mother and the other comes from the father. The first 22 pairs are the same between men and women. The last pair determines our gender. Two X chromosomes makes someone female and an X and Y chromosome makes someone male. Any missing or extra genetic material generally results in incorrect development and function of an individual.
One way to think about chromosomes and genes is to use an analogy of an instruction manual. The manual contains the body's instructions for how to develop and function properly. The chromosomes are like the chapters in the manual and the genes are like the sentences in the manual.
There are many genes that are involved in making the heart form. Gene alterations (or mutations) are changes that cause the gene to stop working properly. If there is an alteration in a gene that is responsible for making the heart form, it is possible that the heart could form differently than expected. The result could be a small hole in the heart or a more complex type of congenital heart defect like tetralogy of Fallot.
Not only are there a large number of genes involved in making the heart form, researchers do not yet fully understand how the genes interact with each other. To explore a possible genetic origin to congenital heart defects, researchers must try to understand the role of each gene in the heart and also how the different genes interact.