Alaika Lehen
Mohamed
Kornelia
Mytsak
Maria Llorca
Roman
AUTOSOMAL
RECESSIVE
DISEASES
§ An autosomal recessive disorder means two copies of an abnormal gene must be present
in order for the disease or trait to develop.
§ Mutations (or changes in the DNA that codes for a gene) have occurred over time in
different parts of the world. Anyone can carry virtually any type of recessive gene;
however, there may be certain ethnic groups more likely to carry certain recessive genes,
because of where the mutation originated.
§ People with only one defective gene in the pair are called carriers. These people are most
often not affected with the condition. However, they can pass the abnormal gene to their
children.
§ If you are born to parents who carry the same
autosomal recessive change (mutation), you have a 1
in 4 chance of inheriting the abnormal gene from both
parents and developing the disease.You have a 50%
(1 in 2) chance of inheriting one abnormal gene.
§ Is one of the most common inherited single gene disorders
in Caucasians.
§ People with CF secrete abnormal body fluids, including
unusual sweat and a thick mucus which prevents the body
from properly cleansing the lungs.The mucus interrupts the
function of vital organs and leads to chronic infections.
§ Classic CF also involves the pancreas and causes decreased
absorption of essential nutrients. Life expectancy has
improved, but, ultimately, death most often occurs from
respiratory failure. Other people with variants of CF may have
only lung involvement, sinusitis, or infertility.
§ SCD is an abnormality in the oxygen carrying protein, Haemoglobin in
erythrocytes. SCD occurs when a person inherits two abnormal copies of the
ß-Globin gene, found on chromosome 11, from each parent.
§ People diagnosed with SCD have atleast one of their ß-Globin subunit in
Haemoglobin A replaced to Haemoglobin S (Hgb S). In sickle cell anaemia
(common form of SCD), both ß-Globin subunits are replaced by Hgb S.
§ A person who only carries one copy of the abnormal gene has Sickle Cell
Trait, they are not severely symptomatic.
§ This change to Hgb S causes the erythrocytes to be rigid and sickle shaped.
causing loss of elasticity of the cells, and therefore loss of ability to pass
through small capillaries easily causing vessel occlusion and ischaemia. An
attack can be induced by stress, temperature changes and high altitudes.
§ SCD occurs more commonly in people who live in tropical regions or who
have ancestors form this region, where malaria is or was common. People with
sickle cell trait confer a heterozygote advantage, they show less severe
symptoms when infected with malaria.
§ Is a rare and fatal genetic disorder that causes
progressive damage to the nervous system.
§ The disease is characterized by destruction of nerve
cells (neurons) in the brain and spinal cord.
§ Caused by a genetic mutation in HEXA gene on
chromosome 15, which codes for hexosaminidase A
enzyme.The recessive autosomal mutation which
leads to disruption in the enzyme and build up of the
molecule GM2 ganglioside within cells in the CNS.
§ There are 3 forms of the disease: Infantile, juvenile and late-onset.
§ the most common form of this disease is infantile Tay-Sachs disease, which
becomes noticeable at around 3-6 months.The symptoms present are the baby has
a loss in ability to crawl, sit or turn over.
§ However as the diseases progresses the symptoms get worse, to seizures, inability
to move, hearing loss, blindness and inability to swallow.
§ initial testing involves an enzyme assay to measure the activity of hexosaminidase.
§ Patients positive for Tay-Sachs disease have a decrease in total hexosaminidase
enzyme activity.