A List of Autosomal Recessive Traits

Years ago, people all over the world married close family members, hoping to keep possessions within the family. Only when deleterious patterns began emerging in descendants did societies review the practice of mating with kinfolk, known as inbreeding. Despite repeated warnings from scientific and religious circles, some communities condone inbreeding; two out of every five states in America allow cousins to marry. Autosomal recessive disorders occur when offspring express masked traits governed by abnormal genes present on any of the first 22 pairs of chromosomes, which excludes the X and Y, or sex, chromosomes.

Mechanism of Inheritance

• A child receives half her genes from her mother and half from her father. Some genes' forms, called "alleles," dominate over others; if a person has one dominant allele, the hidden, or recessive, allele does not show. All humans carry various recessive alleles-coding for nonfunctional or abnormal proteins that produce lethal conditions. Two closely related people often carry the same detrimental recessive alleles, but do not exhibit the trait because they also possess the normal, dominant allele. When the two people procreate, they can pass the same recessive allele to their child, creating a devastating illness.

Albinism

• People with albinism produce little melanin in their eyes, hair and skin. Albinism occurs when a person inherits two defective alleles coding for a gene essential in producing melanin, the pigment occurring in certain human cells. People affected by albinism exhibit different degrees of coloring. Some will have no color at all, others show limited coloring and still others lack pigmentation only in the retina; the layer at the back of the eyes. Albinism leaves people susceptible to deadly skin cancers because melanin absorbs the sun's harmful rays. Treatment includes dealing with individual eye issues that occur in conjunction with albinism. People lacking pigmentation live normal lives, but may experience a lifetime of ridicule if they live among dark-skinned populations.

Cystic Fibrosis

• Two abnormal copies of a gene on Chromosome 7 cause mucus to build up outside lung cells, increasing the susceptibility to bacterial infection in the lungs. Mucus also clogs passages in the pancreas, decreasing the production of chemicals that break down food. Affected individuals often do not live long, usually dying in their early 30s. No treatment exists, but supportive measures such as inhaler antibiotics and physical therapy for the chest improve the quality of life for people with cystic fibrosis.

Fanconi Anemia

• Fanconi anemia targets the bone marrow that produces blood cells.

  Sufferers of Fanconi anemia cannot produce enough blood cells or form abnormal cells in response to their bodies' needs. Fanconi anemia affects the bone marrow, the spongy substance found within the long bones of the body. Bone marrow produces three types of blood cells: red blood cells that transport oxygen and carbon dioxide to and from the body's cells, white blood cells that defend against foreign invaders and platelets that aid in blood clotting. Patients become sick and do not recover completely from infections or injury. Approximately one-tenth of people with this anemia also suffer from leukemia, a cancer affecting white blood cells. Some sufferers enter the world burdened with defects, with many succumbing to the condition during their 20s. Bone marrow transplants and stem cell treatments offer patients hope for longer lives.

Galactosemia

• Babies born with galactosemia cannot process the sugar in milk.

  Milk contains a type of sugar called lactose, which breaks down into the simpler sugars, glucose and galactose, by substances called enzymes. People born with the condition, galactosemia, lack an enzyme located on Chromosome 9 that changes galactose into a form the body can use. Newborns feel the effects most keenly because they rely on milk as their primary sustenance. Without the enzyme, infants grow at a delayed rate, exhibiting abnormalities in the eyes, liver and kidneys. When galactose or its alternate form accumulates in the brain, crippling disabilities result, and death often occurs. Monitoring and managing the intake of milk and milk products help sufferers lead normal lives.

Xeroderma Pigmentosum

• Ultraviolet light from the sun can prove fatal to people with xeroderma pigmentosum.

  Victims of Xeroderma Pigmentosum can never feel the warmth and light of the sun because their bodies cannot repair the damage caused by the sun's ultraviolet rays. People with the disease report eye abnormalities, anomalous skin conditions and skin cancer occurring before 5 years old. Sufferers barricade themselves in darkened homes, apply extra-strength sunscreens, wear restrictive clothing and don protective eyewear. Even with these precautions, many patients die in early adulthood.