Genetics 101

What are Genes?
Genes are the fundamental units of heredity—they provide the instruction for a particular trait such as hair or eye color. Genes are made up of a chemical called deoxyribonucleic acid, or DNA. Each gene contains the information needed for making a specific protein, and each protein has a particular function in the body, such as manufacturing enzymes for biochemical processes.


What are Chromosomes?
Chromosomes are the structures in which genes are packaged. Chromosomes come in pairs, and there can be hundreds and even thousands of genes on one chromosome. Every cell has a total of 46 chromosomes, each with 23 pairs. Half of your chromosomes come from your mother and other half from your father. The first 22 pairs are referred to as autosomes because they are the same between males and females, but the 23rd and final pair are called sex chromosomes because these determine our biological sex. Males have an X and a Y chromosome while females have two X chromosomes.


What are Genetic Disorders?
Every person has two copies of every gene, one inherited from their mother and one from their father. Gene disorders arise when one or both copies of a specific gene have undergone a change or mutation. When a mutation in just one copy of a gene is sufficient to cause a disease, that disorder is considered dominant. When a mutation in both copies of a gene is required to cause a disease, that disorder is considered recessive

Autosomal Dominant Inheritance
In dominant conditions, individuals who have a mutation in one copy of a gene are affected by the disorder, or they are at an increased risk of developing the disorder. Dominant conditions are often inherited from affected parents. Parents pass down one copy of each of their genes to their children. This means the child of someone with a dominant genetic condition  has a 50% chance of inheriting the genetic mutation and the disorder, and a 50% chance of inheriting the functional copy of the gene.

Sometimes a dominant mutation can appear in an individual even if neither parent has the mutation. Such occurrences, referred to as “de novo” mutations, arise when a new mutation occurs in a sperm or egg cell, or in the fertilized egg itself.

Autosomal Recessive Inheritance.

In recessive conditions, individuals are affected if both copies of the gene associated with the disease have a mutation. Someone with a mutation in one copy of a disease causing gene is known as a carrier. Carriers do not have the genetic condition themselves, but are at risk of passing on the condition to their children.

In order for an individual to have mutations in both copies of a gene, one mutation must be inherited from each parent. Two partners who are carriers for the same recessive condition are at risk for having a child with the condition. In each pregnancy, a carrier couples has a 25% chance of having a child with the disorder, a 50% chance of having a child who is a carrier, and a 25% of having a child who is neither affected or a carrier.

Carriers of autosomal recessive disorders often have no family history of the disorder, because these conditions require both parents to be carriers, and carriers are typically healthy.

X-linked Recessive Inheritance (Sex-Linked Inheritance):

A gene that is X-linked is located on the X chromosome. Women have two X chromosomes, while men have one X chromosome and one Y chromosome. In most cases, women who have a mutation in an X-linked gene are not affected because they have a second functioning copy of the gene. Since men have only one X chromosome, they have no such ‘backup’ copy, and are more likely to be affected with an X-linked recessive disorder. It is possible for women to be affected by X-linked recessive disorders as well, thought symptoms are typically less severe. Women are also more likely to be carriers of X-linked conditions, since they can have a mutation in an X-linked gene without experiencing symptoms themselves. X-linked recessive conditions are usually passed down from carrier mothers to sons.

Approximately 1 in 4 Jews is a carrier for one of 56 "Jewish" genetic disorders, included in the Center's carrier screening panel. 

More than half of program participants is a carrier of at least one of the more than 190 genetic disorders the Center's screening panel.


We are proud to announce that our Carrier Screening Program is open with our new medical provider Insight Medical Genetics (IMG). Visit our Get Screened page to learn more about our program and how to register!


Do You Know What's In Your Genes?

What is the most valuable gift you can give to your family? The gift of good health! There are many health conditions that run in families. Knowing your family health history can alert you to the potential risk for a variety of genetic disorders . Be sure to check with your relatives for warning signs and assess your risk for hereditary cancers!

Did you know: Ashkenazi Jews are 10 TIMES more likely to have BRCA mutations, which significantly increases lifetime risks for hereditary cancers, so what does this heightened risk mean for you? Click here to learn more !