A genetic disorder is a disease that is caused by a change, or mutation, in an individual's DNA. Genetic mutations happen when there is a mistake made in the DNA sequence or chromosome causing the wrong amino acid or group of amino acids to be placed into a polypeptide chain. Polypeptide chains bond and fold into a specific shape to form a particular protein. If the wrong amino acids are placed into this chain, then a different or altered protein will be made. According to the National Human Genome Research Institute, "Genetic disorders can be caused by a mutation in one gene (monogenic disorder), by mutations in multiple genes (multifactorial inheritance disorder), by a combination of gene mutations and environmental factors, or by damage to chromosomes (changes in the number or structure of entire chromosomes, the structures that carry genes).- (Genome.gov. 2018. Genetic Disorders. [online] Available at: <https://www.genome.gov/For-Patients-and-Families/Genetic-Disorders> [Accessed 18 May 2018]). Mutations that occur within a single gene (DNA sequence) and will only affect one protein are called Single DNA strand mutations. Point mutations, Frameshift mutations, Duplication mutations, and Inversion mutations all only affect one strand of DNA. These mutations can be beneficial or non beneficial to the organism and their species. A beneficial mutation create a more fit and stable organism. These "good" mutations are what drive evolution. On the other hand, non beneficial or bad mutations can lead to an unhealthy organism which is unfit for their environment. Most mutations go unnoticed when they are an advantage to a species, but are recognized when they cause diseases and syndromes. There are four types of mutations: deletion, insertion, duplication, and inversion. Deletion is when a single nucleotide, group of nucleotides, piece of a chromosome, or whole chromosome is deleted or missing from the organism’s genome. An example of a genetic disorder that is caused by chromosomal deletion is Angelman syndrome. Next is insertion. Insertion is when a single nucleotide, or a group of nucleotides is added into a DNA strand. Insertion is also when a piece of a chromosome or whole chromosome is added into an organism’s existing chromosomes. When a single nucleotide, a group of nucleotides is duplicated within a DNA strand or a piece of a chromosome or whole chromosome is duplicated in an organism’s genome, a duplication mutation happens. Inversion is when a single nucleotide, a group of nucleotides is flipped and reinserted into a DNA strand or a piece of a chromosome is flipped and reinserted into an organism’s existing chromosome.
Some examples of genetic disorders are:
Some examples of genetic disorders are:
- Sickle Cell Anemia: Point mutation- The point mutation causes (blood) hemoglobin to have “sticky” ends and stick together when red blood cells are not carrying oxygen which causes them to elongate into the sickle shape.
- Cystic Fibrosis: Frameshift mutation- An inherited disease characterized by the buildup of thick, sticky mucus that can damage many of the body's organs. It is inherited in an autosomal recessive pattern. It results in salty skin, greasy stool, phlegm build up in lungs, poor growth.
- Progeria: An inversion genetic disorder that causes premature aging in people. Children affected by this disorder experience the same degenerative ailments as the elderly and die from things such as heart attacks and strokes. Progeria shortens the lifespan of patients to only 11-19 years.
- Downs syndrome: a genetic condition in which a person has an extra chromosome. Some effects of Downs syndrome are mental retardation, developmental delays, shorter stature, and some organ dysfunction. Modern medicine and special care has helped to increase life span.
- Hemophilia: Sex-linked genetic disorder on the X chromosome which affects blood clotting factors. People with hemophilia are at a high risk for bleeding to death.
- See the presentation I made below to learn about Phenylketonuria!