DNA is made up of a series of chemicals called nucleotide bases, which link together to form strands of DNA. These strands pair with other DNA strands to form a structure called the double helix. The sequence of nucleotide bases comprises thousands of genes, which in turn code for thousands of proteins. The genes are arranged along 23 chromosomes, and a pair of each chromosome is present in most cells. Genetic mutations can involve deletion or modification to the chromosome, or small genetic changes within specific genes. Genetic mutations commonly lead to absent or dysfunctional proteins, which lead to disease.
Duchenne Muscular Dystrophy
Duchenne muscular dystrophy, also called pseudohypertrophic muscular dystrophy, is a genetic disorder characterized by progressive muscle weakness. Duchenne muscular dystrophy is caused by a mutation to the gene dystrophin, which is essential for proper muscle functioning. The disease is considered an X-linked disorder, meaning that the mutations that cause Duchenne muscular dystrophy occur on the X chromosome. All copies of the X chromosome must be mutated in order to develop the disease. For this reason, Duchenne muscular dystrophy is more common in males, since inheriting a single mutant gene can cause the disorder, whereas two mutant genes must be inherited for a female to develop the disease. Patients with Duchenne muscular dystrophy experience muscle weakness and progressive difficulty walking, along with mental retardation and fatigue. The University of Maryland Medical Center indicates that Duchenne muscular dystrophy is incurable, but medication can help alleviate the symptoms of the disease.
Down Syndrome
Another genetic disease related to DNA is Down syndrome. Patients with Down syndrome have 47 chromosomes in each cell, instead of 46, due to an extra copy of chromosome 21. Down syndrome can be inherited from the mother or the father, and occurs as a result of improper egg or sperm development. Under normal cases, both the egg and sperm contain 23 chromosomes, so that the fusion of the two cells leads to one normal cell containing 46 chromosomes. In Down syndrome, either the egg or sperm contains two copies of chromosome 21, so the fusion of the egg and sperm creates a cell with 47 chromosomes.
Children with Down syndrome experience mental retardation and learning disabilities, as well as craniofacial abnormalities, reports the University of Utah. Patients with Down syndrome face an increased risk for medical problems such as heart defects, hypothyroidism and leukemia. In general, patients with Down syndrome have a shortened lifespan, with only 50 percent of patients living beyond 50 years old.
Sickle Cell Anemia
Sickle cell anemia, also called sickle cell disease, is a genetic disorder characterized by abnormal and dysfunctional, sickle-shaped red blood cells. Under normal conditions, red blood cells function to carry oxygen from the lungs to various tissues throughout the body. Oxygen binds to a compound called hemoglobin, which is found in red blood cells, and the hemoglobin facilitates oxygen transfer throughout the body. Patients with sickle cell anemia carry a a mutation on chromosome 11 that leads to a mutant form of hemoglobin, called HbS, reports the University of Maryland Medical Center. The mutation interferes with normal hemoglobin function, and also changes the shape of the red blood cells, leading to difficulty in carrying oxygen to tissues. Patients with sickle cell anemia have most or all of their hemoglobin mutated, so they experience severe symptoms, such as anemia or stroke, that can prove fatal.
