Genetics and Hereditary Disorders
Genetics (the science of heredity) is a field of biology that focuses on understanding how traits are transmitted from one generation to another. Traits include characteristics such as physical appearance (eye color, height, and hair type) as well as some illnesses. Genes, located in the chromosomes inside our cells, provide the instructions for traits.
What are Genes and Chromosomes?
46 chromosomes make up each human cell. 23 pairs of chromosomes represent maternal and paternal inheritance. Genes are smaller sections of DNA located on a chromosome, which serve as the "instructions" for the development and functioning of each individual.
How Heredity Works
Heredity (the passing down of traits from parents to offspring) is accomplished via genes, with an example being that traits can either express themselves in an offspring depending on whether they are dominant or recessive (that is, an offspring needs only one copy of a dominant gene from a parent(s) to express the dominant trait). Recessive genes also may be carried by an offspring without expressing their associated traits.
Inherited Diseases
An inherited disease is a genetic disease caused by a defective gene inherited from a parent(s). There are many different types of inherited diseases, with some of the most common being cystic fibrosis, sickle cell anemia, hemophilia, and color blindness. Furthermore, there are a large number of genetic diseases not inherited; they manifest as a result of mutations within the individual during his/her lifetime.
Examples of Inherited Diseases
1) Sickle Cell Anemia: A blood disease that causes red blood cells to contain abnormal properties, resulting in distorted (e.g., curved) or hard blood cells. Sickle cells limit a person's ability to transport oxygen and can also cause pain.
2) Cystic Fibrosis: A reported disorder that involves damage to both the lungs and digestive system and results in frequent lung infections and breathing difficulties.
3) Hemophilia: A bleeding disorder that prevents blood cells from clotting properly, resulting in excessive blood loss due to a minor injury.
4) Color Blindness: A hereditary condition caused by abnormal gene expression, affecting the ability to differentiate specific hues of colors.
Preventing Inherited Diseases
If an individual can avoid becoming a carrier of an inherited disease he/she has at least a 50% chance of passing it on (the other parent will be unaffected). In these cases, as previously stated, this gives rise to hereditary mutations; thus, many forms of cancer, diabetes, and heart disease are a direct result of a combination of inherited and lifestyle/environmental factors.