Biological Science
Genetic Disorders
Research Assignment

A cell mutation is any alteration in a gene from its natural state, it is a change in the DNA sequence and can result from many different things including;
DNA copying mistakes made during cell division throughout the body
Expose to radiation, eg ultraviolet radiation
Expose to certain chemicals
Infection
Some mutations are somatic and develop in the eggs and sperm, these mutations are passed on to any children, hence travelling through generations. An example of hereditary mutation would be Multiple Sclerosis. Other mutations occur in the body, from the process of copying mistakes in cell division or many other situations, an example of this type of cell mutation is cancer.
Canavan disease is a fatal neurological disorder that begins at birth. It is caused by a recessive genetic abnormality. Canavan disease causes a lack of enzyme and the decline is myelin in the brain- hence preventing the proper transmission of nerve signals.
As Canavan disease is a recessive mutation two copies of the mutated cell must be present in order for the condition to have an impact. If a person only has one of these mutated genes the disorder will not affect them, instead they will be a carrier and able to pass it on.
Symptoms of Canavan disease, which appear in infancy and develop rapidly, may include:
Mental retardation loss of earlier developed motor skills feeding difficulties abnormal muscle qualities (stiffness or floppiness)
Abnormally large, poorly controlled head.
Paralysis, blindness or hearing loss may occur. Children with Canavan disease are generally quiet and indifferent.
As there is no treatment of Canavan disease the life expectancy of people with this disease dramatically decreases, to as low as four years old. The average life expectancy for a child with Canavan’s disease is around 10 years old. However there is some variation as some affected people may live in their teens or early 20’s. As a child with this disease the quality of life decreases as your ability to do things decreases. As the motor skills are poorly developed it restricts the child from playing and also places a heavy reliance on the parents. Also as the children with this disease generally do die young it is more of the family that is affected during the aftermath of this disease.
Turner Syndrome is a medical disorder that affects 1 in 2500 girls. Turner syndrome has no known cause, although it is linked to the girl’s autosomatic chromosomes, the sex-linked chromosome. Females are born with two autosomatic 'X' chromosomes; a female with Turner syndrome will have one full X chromosome and be missing the other 'X' chromosome.

A female with Turners syndrome will usually be short in height, reaching a max of 1.5metres other symptoms may include;
Kidney problems
High blood pressure
Heart problems
Thyroid problems
Lack of sexual development
A 'webbed' neck
Abnormal bone development
A female with Turners Syndrome has the same life expectancy as any other female, and are still fully able