Many parents are worried about the possibility of their child having a gene disorder. In some cases, this worry can stem from the fact that a couples fertility issues are the result of a gene disorder they themselves have. Concern for passing on a disorder may result in meeting with a genetic counselor for advice and testing. However, not all gene disorders are caused by genetics. Knowing more about genes and how they contribute to fetal development can help you better understand whether or not your child is at risk.
What is a Gene Disorder?Gene disorders are caused by an altered or flawed gene or set of genes. Gene disorders can be inherited when a child receives an altered gene or abnormal chromosome from her parents or from a combination of genetic and environmental factors. There are four main types of gene disorders: single gene disorders, chromosome abnormalities, mitochondrial disorders and multifactorial disorders. Some common disorders caused by altered genes include cystic fibrosis, sickle cell anemia, hemophilia and Tay Sachs disease.
What are Genes?Every cell in your body contains approximately 30,000 genes. Genes are the chemical units composed of deoxyribonucleic acid (DNA) that influence your physical characteristics, personality and intelligence as well as your susceptibility to disease. Genes are found in the chromosomes of a cell. Each person has 23 pairs of chromosomes, one set you inherit from your mother and the other from your father. The sex chromosomes X and Y determine whether you became a girl (XX) or a boy (XY).
Gene MutationOccasionally, the DNA of genes becomes mutated due to an error in cell division, cells divide too quickly or the number or structures of the chromosomes are altered. For example, the genetic disorder Down syndrome is caused by an extra chromosome in the DNA. People with Down syndrome have 47 instead of 46 chromosomes.
How are Gene Disorders Inherited?A gene disorder can be inherited if a gene mutation occurs in egg or sperm cells during conception, or you have a dominant disease gene in your DNA. Genes can be dominant or recessive. You can develop a gene disorder if you have one copy of a dominant disease gene in a chromosome pair or if you have two recessive disease genes in a chromosome pair.
Most people carry 5 to 10 disease genes in their cells, but they do not have the genetic disorder because they do not have the right combination of genes. Certain disorders, like hemophilia, are considered sex-linked or X-linked because the recessive disease gene is carried only on the X chromosome. Because girls have two X chromosomes they have an extra healthy copy of the gene so they do not develop the disease. But boys only have one X chromosome, so they are more likely to develop the disease.