Download Genetic Disorders Multifactorial inheritance, which is also called

Genetic Disorders
Multifactorial inheritance, which is also called complex or polygenic inheritance.
Multifactorial inheritance disorders are caused by a combination of environmental factors and
mutations in multiple genes. For example, different genes that influencebreast cancer
susceptibility have been found on chromosomes 6, 11, 13, 14, 15, 17, and 22. Some common
chronic diseases are multifactorial disorders.
Examples of multifactorial inheritance include:
heart disease,
high blood pressure,
Alzheimer's disease,
arthritis,
diabetes,
cancer
obesity.
Multifactorial inheritance also is associated with heritable traits such as fingerprint patterns, height,
eye color, and skin color.
HEART DISEASE(Cardiovascular Disease, CVD)
Heart (cardiovascular) disease definition and facts
What is Heart Disease?
Heart disease refers to various types of conditions that can affect heart function. These types
include:
Coronary artery (atherosclerotic) heart disease that affects the arteries to the heart.
Coronary artery disease (CAD), commonly known as heart disease, is a condition in
which cholesterol, calcium, and other fats accumulate in the arteries that supply blood to the heart.
This material hardens forming a plaque that blocks blood flow to the heart. When a coronary
artery narrows due to plaque buildup or some other cause, the heart muscle is starved for oxygen
and a person experiences chest pain known as angina.
Sometimes a piece of a fatty plaque in a coronary artery breaks off or ruptures. When this
happens, a blood clot forms in the area in response to the injury. The clot may block the flow of
blood through the artery, causing a heart attack. Sadly, some heart attacks lead to the heart
stopping completely, a situation known as sudden cardiac arrest. The heart may also start to beat
in a very dangerous rhythm called ventricular tachycardia, which is potentially fatal.
Valvular heart disease that affects how the valves function to regulate blood flow in and
out of the heart
There are several types of valve disease:
Valvular stenosis. This occurs when a valve opening is smaller than normal due to stiff or fused
leaflets. The narrowed opening may make the heart work very hard to pump blood through it. This
can lead to heart failure and other symptoms (see below). All four valves can be stenotic
(hardened, restricting blood flow); the conditions are called tricuspid stenosis, pulmonic stenosis,
mitral stenosis or aortic stenosis.
Valvular insufficiency. Also called regurgitation, incompetence or "leaky valve", this occurs when
a valve does not close tightly. If the valves do not seal, some blood will leak backwards across the
valve. As the leak worsens, the heart has to work harder to make up for the leaky valve, and less
blood may flow to the rest of the body. Depending on which valve is affected, the conditioned is
called tricuspid regurgitation, pulmonary regurgitation, mitral regurgitation or aortic regurgitation.
Valve disease can develop before birth (congenital) or can be acquired sometime during one's
lifetime. Sometimes the cause of valve disease is unknown.
Congenital valve disease. Most often affects the aortic or pulmonic valve. Valves may be the
wrong size, have malformed leaflets, or have leaflets that are not attached to the annulus correctly.
Bicuspid aortic valve disease is a congenital valve disease that affects the aortic valve. Instead of
the normal three leaflets or cusps, the bicuspid aortic valve has only two. Without the third leaflet,
the valve may be stiff (unable to open or close properly) or leaky (not able close tightly).
Acquired valve disease. This includes problems that develop with valves that were once normal.
These may involve changes in the structure or your valve due to a variety of diseases or infections,
including rheumatic fever or endocarditis.
Rheumatic fever is caused by an untreated bacterial infection (usually strep. throat). Luckily, the
introduction of antibiotics to treat this infection has dramatically reduced the numbers of this
infection. The initial infection usually occurs in children, but the heart problems associated with
the infection may not be seen until 20-40 years later. At that time, the heart valves become
inflamed, the leaflets stick together and become scarred, rigid, thickened and shortened. This leads
to mitral regurgitation.
Endocarditis occurs when germs, especially bacteria, enter the bloodstream and attack the heart
valves, causing growths and holes in the valves and scarring. This can lead to leaky valves. The
germs that cause endocarditis enter the blood during dental procedures, surgery, IV drug use, or
with severe infections. People with valve disease (except mitral valve prolapse without thickening
or regurgitation/leaking) are at increased risk for developing this life-threatening infection.
There are many changes that can occur to the valves of the heart. The chordae tendinea or
papillary muscles can stretch or tear; the annulus of the valve can dilate (become wide); or the
valve leaflets can become fibrotic (stiff) and calcified.
Mitral valve prolapse (MVP) is a very common condition, affecting 1 to 2 percent of the
population. MVP causes the leaflets of the mitral valve to flop back into the left atrium during the
heart's contraction. MVP also causes the tissues of the valve to become abnormal and stretchy,
causing the valve to leak. The condition rarely causes symptoms and usually doesn't require
treatment.
Other causes of valve disease include: coronary artery disease, heart attack, cardiomyopathy (heart
muscle disease), syphilis (a sexually transmitted disease), hypertension, aortic aneurysms, and
connective tissue diseases. Less common causes of valve disease include tumors, some types of
drugs and radiation. muscle squeezes
Heart rhythm disturbances (arrhythmias) that affect the electrical conduction
Heart infections where the heart has structural problems that develop before birth
Coronary artery disease is the most common type of heart disease in the US.
Coronary arteries supply blood to the heart muscle and coronary artery disease occurs when there
is a buildup of cholesterol plaque inside the artery walls. Over time, this buildup of plaque may
partially block the artery and decrease blood flow through it.
A heart attack occurs when a plaque ruptures and forms a clot in the artery causing a complete
blockage. That part of the heart muscle that is denied blood supply starts to die.
Classic signs and symptoms of coronary heart
What is high blood pressure?
High blood pressure (hypertension) is defined as high pressure (tension) in the arteries, which are
the vessels that carry blood from the heart to the rest of the body.
Blood pressure readings are given as two numbers. The systolic blood pressure (the top number)
equals the pressure in the arteries as the heart contracts. The diastolic pressure (the bottom number)
is the pressure in the arteries as the heart relaxes. Normal blood pressure is below 120/80; blood
pressure between 120/80 and 139/89 is called "pre-hypertension," and a blood pressure of 140/90
or above is considered high while a systolic blood pressure of about 90 to 100 is considered low
blood pressure.
Complications of high blood pressure include heart disease, kidney (renal) disease, hardening of
the arteries (atherosclerosis or arteriosclerosis), eye damage, and stroke (brain damage).
Hypertension is a major public health problem. The American Heart Association estimates high
blood pressure affects approximately one in three adults in the United States, or about 76.4 million
people.
Alzheimer's disease
The History of Dementia
In 1906 Auguste Deter, a woman in her early 50s, became the first person diagnosed with
Alzheimer's disease, a form of dementia. The disease is named after the doctor who first described
it, Alois Alzheimer. The disease is characterized by odd behavior, memory problems, paranoia,
disorientation, agitation, and delusions. After Deter’s death, Alzheimer performed a brain autopsy
and discovered dramatic shrinkage and abnormal deposits in and around nerve cells.
In 1910 the term “Alzheimer’s Disease” was formally used. In 1974 Congress established the
National Institute on Aging (NIA), the primary federal agency supporting Alzheimer’s research.
Types of Dementia
There are several different classifications of dementia. Dementia can be classified by either the
area of the brain that is affected, whether it is progressive, or whether it results from another
disorder (primary or secondary).
Cortical Dementias
Cortical dementias occur because of problems in the cerebral cortex, the outer layer of the brain.
This type of dementia plays an important role in memory and language and people with cortical
dementias usually have severe memory loss and can’t remember words or understand language.
Creutzfeldt-Jakob and Alzheimer’s disease are two types of cortical dementia.
Subcortical Dementias
Subcortical dementias occur because of problems in the part of the brain beneath the cortex. The
ability to start activities and speed of thinking are usually effected by subcortical dementias.
Forgetfulness and language problems are typically not developed in subcortical dementias.
Parkinson’s disease, Huntington’s disease, and HIV can cause these types of dementia.
Progressive Dementia
Progressive dementias become worse over time and patients eventually lose more of their abilities.
Alzheimer’s disease, Lewy body dementia, vascular dementia, and frontotemporal dementia are
types of progressive dementia.
Primary Dementia
Primary dementia patients only show symptoms of dementia. Alzheimer’s disease is a form of
primary dementia, which accounts for 50%-70% of all dementia cases.
Secondary Dementia
A secondary dementia is a form of dementia that develops as a peripheral conditions to a
pre-existing mental illness or condition. Brain infections, progressive supranuclear palsy, and
multiple sclerosis are examples of conditions that can cause secondary dementias to form. Many
types of secondary dementias can be stopped or reversed, unlike other types of dementias.
Dementia Stages
Doctors will determine a patient’s stage by asking a variety of questions to the patient and the
caregiver. The Mini-Mental Stage Examination is a screening tool used to identify cognitive
decline on a scale of 0 to 30. Stage diagnosis can help the doctor create a treatment plan.
No Impairment
There are no obvious signs at this stage and people are able to function independently.
Very Mild Impairment
Symptoms at this stage are slight and seem to appear as forgetfulness associated with aging.
Mild Impairment
Patients are still able to do daily routine and tasks. Symptoms include the following:
Forgetfulness
Memory loss
Losing items
Trouble managing finances
Confusion while driving
Trouble managing medications
Loss of concentration
Moderate Impairment
Patients typically have trouble performing daily routine and tasks. Symptoms include the
following:
Trouble holding urine
Increased memory loss and forgetfulness
Inability to use or find the correct words
Difficulty doing challenging mental math
Increased social withdrawal
Moderately Severe Impairment
Patients will need assistance in daily routine and tasks. Symptoms include the flowing:
Increased memory loss
Confusion about location or previous events
Trouble with less challenging mental math
Needing help with selecting appropriate wardrobe
Severe Impairment
Patients will need more assistance in daily routine and tasks. Symptoms include the following:
Needing assistance when getting dressed
Needing assistance when using the restroom
Wondering and getting lost
Unable to recall names of loved-ones or caregivers
Sleep disturbances
Changes in personality (paranoia or hallucinations)
Very Severe Impairment
Patients will need constant care. Symptoms include the following:
Loss of language skills
Loss of awareness of surroundings
Assistance when eating
Unable to control urination
Loss of muscle control to smile, swallow, walk, or sit without support
Chromosome abnormalities
Chromosomes, distinct structures made up of DNA and protein, are located in the nucleus of each
cell. Because chromosomes are the carriers of the genetic material, abnormalities in chromosome
number or structure can result in disease. Abnormalities in chromosomes typically occur due to a
problem with cell division.
For example, Down syndrome (sometimes referred to as "Down's syndrome") or trisomy 21 is a
common disorder that occurs when a person has three copies of chromosome 21. There are many
other chromosome abnormalities including:
Turner syndrome (45,X0),
Klinefelter syndrome (47, XXY), and
Cri du chat syndrome, or the "cry of the cat" syndrome (46, XX or XY, 5p-).
Diseases may also occur because of chromosomal translocation in which portions of two
chromosomes are exchanged.
Mitochondrial inheritance
This type of genetic disorder is caused by mutations in the non-nuclear DNA of mitochondria.
Mitochondria are small round or rod-like organelles that are involved in cellular respiration and
found in the cytoplasm of plant and animal cells. Each mitochondrion may contain 5 to 10 circular
pieces of DNA. Since egg cells, but not sperm cells, keep their mitochondria during fertilization,
mitochondrial DNA is always inherited from the female parent.
Examples of mitochondrial disease include:
an eye disease called Leber's hereditary optic atrophy;
a type of epilepsy called MERRF which stands for myoclonic epilepsy with Ragged Red Fibers;
and
a form of dementia called MELAS for mitochondrialencephalopathy, lactic acidosis and
stroke-like episodes.
What is the human genome?
The human genome is the entire "treasury of human inheritance." The sequence of the human
genome obtained by the Human Genome Project, completed in April 2003, provides the first
holistic view of our genetic heritage. The 46 human chromosomes (22 pairs of autosomal
chromosomes and 2 sex chromosomes) between them house almost 3 billion base pairs of DNA
that contains about 20,500 protein-coding genes. The coding regions make up less than 5% of the
genome (the function of all the remaining DNA is not clear) and some chromosomes have a higher
density of genes than others.
Most genetic diseases are the direct result of a mutation in one gene. However, one of the most
difficult problems ahead is to further elucidate how genes contribute to diseases that have a
complex pattern of inheritance, such as in the cases of diabetes, asthma, cancer, and mental illness.
In all these cases, no one gene has the yes/no power to say whether a person will develop the
disease or not. It is likely that more than one mutation is required before the disease is manifest,
and a number of genes may each make a subtle contribution to a person's susceptibility to a
disease; genes may also affect how a person reacts to environmental factors.