Guide to Genetic Services

Talk with your doctor if you are interested in a genetics assessment. Some reasons to get genetic consultation are: 

• Delays in mental and physical development 
• Birth defects 
• Families in which more than one person has the same condition or disorder 
• Couples with multiple miscarriages, stillborns or infertility 
• Abnormal prenatal screen results 
• Exposure to an environmental agent 
• Medications or alcohol use in pregnancy 
• Early onset cancer in the patient or family 

A genetics consultation is the evaluation of a person’s health and family history to see if they have a genetic condition, or genetic predisposition to a health problem. Genetic counseling gives the patient the chance to have a talk with a trained health professional to discuss their risk for a genetic disease and to figure out if they want to get further testing. A physical exam may be done to look for symptoms of a certain genetic condition. One of the goals of the consultation is to confirm, diagnose or to rule out a genetic condition. During the appointment the patient will be given information on the limitations, benefits and risks of a genetic test. Genetic professionals will also talk to the patient about how to deal with medical issues related to the genetic condition or genetic predisposition. They also give families information about genetic disorders and possible genetic testing and provide education about testing procedures, diagnosis, prognosis, available options, recurrence risks and support services. Genetic professionals are trained to help patients understand genetic inheritance patterns and what causes the specific genetic condition. 

Genetic testing involves a laboratory test to look at a person’s genetic material in their body. This can involve looking at the DNA, RNA, chromosomes, proteins or certain metabolites. This is usually done with a blood, saliva or tissue sample. It can also be done in a pregnancy with amniotic fluid and chorionic villi. Genetic testing should only be done after genetic counseling to ensure that the patient understands the benefits and limitations of the specific test that is ordered. It is important to note that genetic test results can apply not only to the patient but may also give information about other family members. Genetic tests are usually done by special labs.

Genetic professionals are medical geneticists, genetic counselors and genetic nurses. A medical geneticist is a doctor who specializes in the diagnosis and treatment of genetic disorders. Most medical geneticists are pediatricians, internists and obstetricians that have received at least an additional two years of training in clinical genetics and are board certified by the American Board of Medical Genetics. Genetic counselors are professionals who have a master’s degree in genetic counseling and are certified by the American Board of Genetic Counseling. Genetic counselors are trained in explaining genetic information to families. 

What caused the specific genetic condition or genetic predisposition in the family? What are the features of the genetic syndrome? How is this condition treated? Could it happen again to another child? Is there a genetic test that could confirm the diagnosis? How accurate is the genetic testing for this condition? What are the support services available in the area for this condition? Is there financial help available for individuals with this condition? Are you a board certified genetic counselor or medical geneticist? 

These services are provided by a group of health care professionals that are specifically trained and board certified in medical genetics. They include medical geneticists, genetic nurses and genetic counselors. Genetic professionals practice throughout Texas. There are over 150 board certified genetic professionals in Texas working in about 70 clinics and hospitals. Some genetics professionals specialize in certain areas, such as children, pregnant patients, adults or families at risk for cancer. Find a provider in your area.

Knowledge of a genetic condition or predisposition can change your medical and life choices. Prevention is the key to many health conditions. Genetic testing can give you information to make good health choices.

Your body is made up of trillions of cells. In each cell there are normally 46 chromosomes. We get 23 chromosomes from our mother and 23 chromosomes from our father. Thus, our chromosomes come in pairs. The chromosomes are made up of DNA. The DNA or deoxyribonucleic acid is a chemical code or instructions that direct how your body is developed. Each chromosome has very specific chapters that tell the cell what kinds of characteristics you will have (like eye color and hair color). Each of these chapters that code for a specific trait is called a gene. Genes are small pieces of DNA that have information about your traits. 

Genes, like the chromosomes, come in pairs. Each person receives one copy of a gene from their mother and one from their father. Even though you get half of your genes from your mother and half from your father, sometimes one gene is dominant over the other gene. An example would be the genes for eye color. The gene that gives you brown eyes is dominant over the gene that gives you blue eye color. Dominant genes are always expressed, regardless of what the other gene is that a person has. A person with brown eyes can have either two “brown” genes or one “brown” gene and one “blue” gene. People with blue eyes must have two copies of the “blue” gene (one from each parent). When you need two copies of a non-dominant gene to express the trait, it is called a recessive trait. If a person has one dominant gene and one recessive gene, they are called a carrier. This is because they express the dominant trait, but "carries" the recessive gene. It is possible for two brown eyed parents to have a blue-eyed child if both parents are “carriers” for the recessive gene. Many genetic conditions are also inherited this way, such as: Cystic Fibrosis, Sickle Cell Anemia and Tay Sachs Disorder. These are genetic conditions that are due to recessive genes. These conditions have an equal chance of appearing in both males and females. 

Genetic disorders can result when there is a mistake in the genetic code of a single gene. Genes carry the bits of information which determine the growth and function of a person. Genes are like recipes to build everything in our bodies. We have two copies of every gene, one from the mother and one from the father. Some genetic conditions result when there is only one of the gene pairs that has been changed or altered. A dominant condition is when one gene is changed, and it affects health, growth, or development. If both genes are mutated before a patient has symptoms, it is called a recessive condition. An example of a single gene disorder that is inherited as a dominant disorder is Huntington’s Chorea. Sickle cell anemia is a genetic disorder that is inherited as a recessive condition. Single gene disorders are inherited by different patterns of inheritance; autosomal dominant, autosomal recessive, and x-linked. Learn more about the genetic inheritance patterns.

Each of our body’s cells have 46 chromosomes. Each of the chromosomes is made up of thousands of genes. The first 22 pairs of chromosomes are identical and are called autosomes. The last pair of chromosomes is called the sex chromosomes. In males there is a Y chromosome and one X chromosome. In females there are two X chromosomes. Genetic disorders can occur when there are extra or missing chromosomes. It is also possible that only part of a chromosome is missing, or a rearrangement has happened between chromosomes (translocation). Any time there are missing or extra chromosomes, birth defects and/or mental retardation can occur. An extra chromosome would mean that there are thousands of extra copies of genes. A missing chromosome would mean there are missing genes. 

Down syndrome is a genetic condition that is caused by an extra copy of the 21st chromosome. Before parents can make a baby, certain cells in the ovaries and sperm must divide so that the child does not get too much DNA. Each cell that will make the baby must have exactly 23 chromosomes. When the cell from the mother (the egg) merges with the cell from the father (the sperm), the baby will have its full 46 chromosomes. These parental cells must go through a very specific kind of division called meiosis where new cells have exactly half the genetic material. During this division, chromosomes that encode the same kinds of genes must line up next to each other. They then split away to the 2 new cells. 

Sometimes they "stick" together, leaving one cell with one extra and one cell with one fewer chromosome. This is called nondisjunction. Then the baby will have too many or not enough chromosomes when the sperm and egg merge. This is what happens in Down Syndrome. Chromosome 21 doesn't separate properly. The child then gets one extra chromosome from either the mother or the father. Instead of having 2 copies, the child gets 3.

Genetics is related to cancer in that cancer results from mutated genes. Sometimes these genes are passed down through families putting them at greater risk for getting cancers. Three major events happen to turn a normal cell into a cancerous (or malignant) one.

1. Dividing out of control 
   When a cell divides, it must get the OK from certain molecules (proteins) on its surface. These substances help regulate the cell, so it does not divide too much. Specific genes are responsible for making these proteins. If these genes have defects, or mutations, in them, they produce defective proteins. Defective proteins lose their ability to perform their job correctly. The cell then begins to divide more than it should. 

2. Lose awareness of surrounding cells 
   Like the proteins that help control how a cell divides, other proteins are involved in letting a cell know that other cells are around. This helps cells to know how much space it has to grow and when it should slow down or stop. Mutations in these proteins cause cell growth to spill over into surrounding tissue. This creates a tumor where cells grow on top of each other instead of in a single layer. 

3. Lose ability to stay put 
   Though the first two events may happen, cancer might not result, like a mole. This is an example of a benign tumor. When a tumor is malignant, it has gained the ability to spread throughout the body. Cancerous tumors can cause blood vessels to grow toward them. Then some of the cells can move to other areas of the body by traveling in the blood. This is called metastasis. Since other proteins help a tumor "metastasize", it results from mutations in genetic material.