Genetic Disorders

INTRODUCTION

What is genetic diseases/disorders?

The human body is composed up of cells , each one specializing a

particular function like sensing light, smelling etc, So the chromosomes

which are the sub cellular structure that exist in the nucleus of each cell

that makes a human body .There are 23 pairs of chromosomes in

human, these chromosomes are responsible for transferring genetic

information from one generation to another.

Most people have the concept that genetic disease must be the

one which is transmitted from one generation to next. Actually this is

not totally correct. In medicine genetic disease refers to one that is

caused by abnormalities of the genetic material at the stage of germ

cells or early embryo.

CATEGORIES OF GENETIC DISORDERS

a) Chromosomal Disorder: Abnormalities in chromosome

structure such as missing or extra copies.

b) Single Gene Disorder: Disorders caused by abnormality or

mutation in the sequence of a single gene. The pure genetic

diseases are caused by a single gene in the human DNA. These

are classified as Dominant, Recessive and X-linked diseases.

c) Multifactorial Disorders: That are caused by the result of the

combined effect of genetic and environmental factors.

d) Mitochondrial Disorders: Caused by mutation in the non

chromosomal DNA of mitochondria.

COMMON GENETIC DISORDERS

• Gaucher Disorder

• Huntington’s Disorder

• Hemophilia

• Parkinson’s Disorder

• Sickle Cell Anemia

• Cystic Fibrosis

• Down Syndrome

• Alzheimer’s Disorder

• Thalassemia

• Tay-Sachs Disorder

GAUCHER DISORDER

• Gaucher disease is a genetic disorder handed down from

generation to generation

• It is most common of a genetic disorder

• Caused by the deficiency of an enzyme β-glucocerebrocidase

• When there is not enough of the enzyme , the fat can not be

broken down and is stored primarily in the liver and spleen.

• Other body organ, tissues and bones are also effected , in rare

cases it may also accumulates in the brain.

• Its symptoms are;

• Bone pain and fractures, Seizures, Liver and spleen enlargement

and fatigue.

HUNGTINGTON’S DISEASE

• It results from genetically programmed degeneration of nerve

cells in certain areas of the brain

• This degeneration causes uncontrolled movements , loss of

intellectual faculties

• Emotional Disturbance

• The Symptoms of this disease are ;

• Mood Swings, irritability , depression, loss of memory and

uncontrolled movements

• As this disease progresses walking and speech become more

difficult, the memory and intellectual functions continue to

decline.

HEMOPHILIA

• Hemophilia is the oldest known bleeding disorder.

• It is sex-linked disorder, b/c of which it appears mostly in males.

• Hemophilia is like any other sex-linked disorder, b/c the hemophilia gene is on the X chromosome.

• 2 types of hemophilia;

• Hemophilia A: Lack of the blood clotting protein factor VIII.

• Hemophilia B: Lack of the blood clotting protein factor IX.

• Symptoms;

• Main symptom is once bleeding starts the child bleeds longer than normal.

• It may include; Nosebleeds, bleeding for no reason, blood in the urine or stool and bleeding into a joint, which can cause tightness, swelling and pain.

PARKINSON’S DISEASE

• Parkinson’s disease is a neurological condition that has a genetic component next to Alzheimer’s.

• The chances of getting developing Parkinson’s gets higher as age increases.

• Causes of Parkinson; DOPAMINE chemical produced in the middle part of the brain that is responsible for organizing coordinated movements and to send this signal to the control centers of the brain.

• In Parkinson's chemical production less and functioning starts to shut down slowly and patient begins to lose control over vital voluntary movement.

• Symptoms; Memory loss, blurriness and lack of postural stability.

SICKLE CELL ANEMIA

• Sickle cell anemia is blood related disorder that affects the

hemoglobin molecule and causes the entire blood cell to

change shape under stressed conditions.

• In sickle cell anemia hemoglobin molecule is defective.

• Round form of blood cells changes into long, rod-like

structures which become stiff and assumes sickle shape

so cell failed to carry oxygen.

• Normal red blood cells live 120 days in the bloodstream,

but sickled red cells die after about 10 to 20 days.

• Symptoms; Lung and heart damage, eye damage,

arthritis and fatigue etc.

THALASSEMIA

• It is a blood related genetic disorder which involves the

absence or errors in genes responsible for production of

hemoglobin.

• The severity of disease depend on the mutations involved

in the genes and their interplay.

• Hemoglobin has 2 sub units referred as alpha and beta,

chromosome 16 responsible for alpha sub unit and

chromosome 11 for beta sub unit, lack of particular sub

units determine the type of thalassemia.

• Symptoms; Reduce fertility or even infertility, jaundice,

paleness, poor appetite

CYSTIC FIBROSIS

• An inherited disease that affects sodium and chloride channels

in the body and causes respiratory and digestive problems.

• It is monogenic and caused by mutation in a single gene on

chromosome 7.

• Gene contains building information for CFTR (cystic fibrosis

trans-membrane conductance regulator)

• CFTR is a protein that in humans is encoded by the CFTR

gene,and due to mutation it becomes non-functional.

• Usually diagnosed at birth and occurs both in males and

females.

• Symptoms;

• Excessive production of mucus in air tract, poor appetite,

tiredness etc.

TAY SACHS DISEASE

• Tay-sachs disease is a fatal genetic disorder in which

harmful quantities of a fatty substance called Ganglioside

GM2 accumulate in the nerve cells in the brain.

• This is caused by a decrease in the functioning of

Hexosaminidase A enzyme.

• Its abnormal activities causes an accumulation of fat in

the nerve cells leading to paralysis, dementia, blindness

and even death.

• This disease/disorder is autosomal recessive which

means that an individual must inherit both the two

defective genes, one from each parent.

ALZHEIMER’S

• Alzheimer's is a form of dementia that causes changes in

the brain.

• Also affects a person’s memory, mood and behavior.

• Disease mostly affects people over 65.

• There is no specific test for Alzheimer disease however

physician are able to look at a person medical history and

give a physiological and memory tests to see how efficient

the brain is.

• Symptoms;

Memory loss etc

DOWN SYNDROME

• Down syndrome is caused by an extra chromosome

present on chromosome 21.

• Down syndrome is caused by mutations.

• Form of down syndrome;

• Klinefelter’s syndrome also known as the XXY

condition, is a term used to males who have an extra X-

chromosome in most of their cells.

• Turner’s syndrome is a chromosomal condition related

to the X-chromosome that alters development in females.

It leads to infertility, webbed neck, skeletal abnormalities,

heart defects and kidney problems.