Genetic Disorders caused by mutations found in DNA

Sickle Cell Disease

 Sources: http://creationwiki.org/Sickle_Cell_Anemia

Sickle cell disease is caused when a person inherits 2 copies of the sickle cell gene, one from each parent. It affects the shape of the red blood cell as it affects the haemoglobin, which is found in the red blood cells. A normal red blood cell with normal haemoglobin would be able to pass through the blood vessels easily. However, the red blood cells of a person with this disease would not be able to pass through the blood vessels easily. This is because the haemoglobin has been altered, and thus altering the shape of the red blood cell. As red blood cells cannot pass through the blood vessels easily, clogging of the blood vessels happen often. Complications include anemia, whereby there is a shortage of red blood cells to carry oxygen around the body; aplastic crisis, which occurs when the body does not make red blood cells; stroke and splenic sequestration crisis, where the spleen becomes enlarged due to the entrapment of red blood cells.

Down Syndrome

Picture showing the chromosomes of a boy (X and Y Chromosomes) with down syndrome (3 copies of chromosome 21).
Source: http://downsyndrome.com/

Down syndrome is caused when a person has an extra copy of chromosome 21. Normal people would have 46 chromosomes (23 pairs), however, people with down syndrome, having an extra copy of chromosome 21, would have 47 chromosomes. As this causes them to have 3 copies of chromosome 21, Down Syndrome is also known as Trisomy 21. Down Syndrome is not commonly inherited. The only time when Down syndrome is inherited is when translocation occurs. This means that they have an extra chromosome 21 joined to other chromosomes. Down syndrome causes people to have mental retardation, meaning that they learn at a slower pace than normal people. This is why schools have been set up for children with down syndrome. Physical features of people with down syndrome are easily recognizable, for example, flattened face, almond shaped eyes and reduced muscle tone. Down syndrome can also cause heart defect and digestive system defect.

Haemophilia
Hemophilia is an inherited genetic disorder which affects the rate at which an affected person heals. This is because it affects the protein which helps the blood to clot. Haemophilia is caused by defective genes that determines how the body makes clotting factors VIII and and IX. The genes are found in the X chromosomes, which also determines the sex of a human being. A person (also known as a haemophiliac) with haemophilia will take longer time to heal than a person without haemophilia. Furthermore, people with haemophilia may suffer from internal bleeding in the joints, knees,etc. Haemophilia usually happens in males, with very rare exceptions.

Types of haemophilia:
- Type A: clotting factor VIII is missing or low. Most haemophiliacs have this type of haemophilia.
- Type B: clotting factor IX is missing or low.

Bibliography:
1.http://www.wikipedia.org/
2.https://www.labcorp.com/genetics/
3.http://www.medic8.com/healthguide/articles/haemophilia.html