Genetic Disorders

by: Mariah Hedrick
7th Period

In this specific tackk,we will discuss eleven (11) different types of genetic disorders. They fit under two categories, sex-linked and autosomal. The genetic disorders are Hemophilia, Tay-Sachs, Sickle Cell Anemia, Muscular Dystrophy,

Hemophilia ( sex - linked )
A rare genetic disorder (inherited) when a person's blood clots very slowly or not at all. It takes much longer for a hemophiliac to stop bleeding in comparison to the average person. Hemophilia can also cause internal bleeding, especially in the joints (ankles, elbows, knees). Babies born with the disorder have a low amount of a certain protein or don't have the protein that is needed for blood to clot (protein is referred to as a "clotting factors"). Hemophilia is also sex-linked.

Symptoms include:

  • Nosebleeds
  • Bruising, especially a large, lumpy bruise
  • Bleeding for no known reason
  • Blood in the urine or stool
  • Bleeding that does not stop after getting a cut, having a tooth out, getting an injury to the mouth or having surgery
  • Bleeding that does not stop after circumcision
  • Bleeding into a joint, which can cause tightness, swelling and pain

Average age & tests used:

In children and adults, a blood test can show a clotting-factor deficiency. Hemophilia is diagnosed at an average age of 9 months and almost always by age 2. Sometimes, mild hemophilia isn't diagnosed until a person undergoes surgery and experiences excessive bleeding.

Color-blindness ( sex-linked )

The inability to distinguish the differences between certain colors. This condition results from an absence of color-sensitive pigment in the cone cells of the retina, the nerve layer at the back of the eye.

Symptoms include:

  • Difficulty distinguishing between colors.
  • Inability to see shades or tones of the same color.
  • Rapid eye movement (in rare cases)

Tests used:

The most commonly used is the American Optical/Hardy, Rand, and Ritter Pseudoisochromatic Test. It is composed of several discs filled with colored dots of different sizes and colors. A person with normal color vision looking at a test item sees a number that is clearly located somewhere in the center of a circle of variously colored dots. A color-blind person is not able to distinguish the number.

Tay-Sachs Disease (sex-linked )

Tay-Sachs is a disease of the central nervous system; it is a neurodegenerative disorder. Tay-Sachs most commonly affects infants. In infants, it is a progressive disease that is unfortunately always fatal. Rarely, Tay-Sachs can occur in teens and adults, causing less severe symptoms.

Symptoms include:

  • deafness
  • blindness
  • decreased muscle tone
  • increased startle response
  • paralysis or loss of muscle function
  • seizures
  • delayed mental and social development
  • slow growth
  • red spot on the macula (an oval-shaped area near the center of the retina in the eye)

Average age and tests:

Prenatal tests, such as chorionic villus sampling (CVS) and amniocentesis, can diagnose Tay-Sachs disease. Genetic testing is generally done when one or both members of a couple are carriers of the disease. It is usually determined at birth.

Sickle Cell Anemia (sex-linked)

In sickle cell anemia, the red blood cells become rigid and sticky and are shaped like sickles or crescent moons. These irregularly shaped cells can get stuck in small blood vessels, which can slow or block blood flow and oxygen to parts of the body.


  • Anemia
  • Episodes of pain
  • Hand-foot syndrome
  • Frequent infections
  • Delayed growth
  • Vision problems

Average age and tests:

Sickle cell anemia is diagnosed at birth. Signs and symptoms of sickle cell anemia often don't appear until an infant is at least 4 months old. Blood tests are usually done to test this.

Muscular Dystrophy (autosomal )

Muscular dystrophy is a group of diseases that cause progressive weakness and loss of muscle mass. In muscular dystrophy, abnormal genes (mutations) interfere with the production of proteins needed to form healthy muscle. Some people who have muscular dystrophy will eventually lose the ability to walk. Some may have trouble breathing or swallowing.

Symptoms include:

  • Frequent falls.
  • Difficulty getting up from a lying or sitting position.
  • Trouble running and jumping.
  • Waddling gait.
  • Walking on the toes.
  • Large calf muscles.
  • Muscle pain and stiffness.
  • Learning disabilities.

Average age and tests:

Muscular Dystrophy is diagnosed in the absence of a family history of DBMD, a delay of 2.5 years occurred from the time the first symptoms were noticed to the time a definite diagnosis of the condition was made. Your doctor is likely to start with a medical history and physical examination. After that, your doctor may recommend enzyme tests, electromyography, genetic testing, muscle biopsy, heart-monitoring tests, and lung-monitoring tests.

Parkinson's Disease (autosomal)

Parkinson's disease is a progressive disorder of the nervous system that affects your movement. It develops gradually, sometimes starting with a barely noticeable tremor in just one hand. But while a tremor may be the most well-known sign of Parkinson's disease, the disorder also commonly causes stiffness or slowing of movement.

Symptoms include:

  • Tremor
  • Slowed movement (bradykinesia)
  • Rigid muscles
  • Impaired posture and balance
  • Loss of automatic movements
  • Speech changes
  • Writing changes

Average age and tests:

Parkinson's disease is a chronic, degenerative neurological disorder that affects one in 100 people over age 60. While the average age at onset is 60, some people are diagnosed at 40 or younger. No tests exist to diagnose Parkinson's disease. Your doctor trained in nervous system conditions (neurologist) will diagnose Parkinson's disease based on your medical history, a review of your signs and symptoms, and a neurological and physical examination.

PKU (autosomal)

A rare inherited disorder that causes an amino acid called phenylalanine to build up in your body. PKU is caused by a defect in the gene that helps create the enzyme needed to break down phenylalanine.

Symptoms include:

  • Intellectual disability (formerly called mental retardation)
  • Delayed development
  • Behavioral, emotional and social problems
  • Psychiatric disorders
  • Neurological problems that may include seizures
  • Hyperactivity
  • Poor bone strength
  • Skin rashes (eczema)
  • A musty odor in the child's breath, skin or urine, caused by too much phenylalanine in the body
  • Fair skin and blue eyes, because phenylalanine cannot transform into melanin — the pigment responsible for hair and skin tone

Average age and tests:

PKU is determined at the time around birth. Newborn blood testing identifies almost all cases of phenylketonuria. All 50 states in the United States require newborns to be screened for PKU. Many other countries also routinely screen infants for PKU. A PKU test is done a day or two after your baby's birth. The test isn't done before the baby is 24 hours old or before the baby has ingested some protein in the diet to ensure accurate results

Huntington Disease (autosomal)

Huntington's disease is an inherited disease that causes the progressive breakdown (degeneration) of nerve cells in the brain. Huntington's disease has a broad impact on a person's functional abilities and usually results in movement, thinking (cognitive) and psychiatric disorders.

Symptoms include:

The movement disorders associated with Huntington's disease can include both involuntary movements and impairments in voluntary movements. Impairments in voluntary movements — rather than the involuntary movements — may have a greater impact on a person's ability to work, perform daily activities, communicate and remain independent. Cognitive impairments often associated with Huntington's disease include:

  • Difficulty organizing, prioritizing or focusing on tasks
  • Lack of flexibility or the tendency to get stuck on a thought, behavior or action (perseveration)
  • Lack of impulse control that can result in outbursts, acting without thinking and sexual promiscuity
  • Lack of awareness of one's own behaviors and abilities
  • Slowness in processing thoughts or ''finding'' words
  • Difficulty in learning new information

The most common psychiatric disorder associated with Huntington's disease is depression. This isn't simply a reaction to receiving a diagnosis of Huntington's disease. Instead, depression appears to occur because of injury to the brain and subsequent changes in brain function. In addition to the above symptoms, weight loss is common in people with Huntington's disease, especially as the disease progresses.

Average age and tests:

Most people with Huntington's disease develop signs and symptoms in their 30s or 40s, but the onset of disease may be earlier or later in life. When disease onset begins before age 20, the condition is called juvenile Huntington's disease. Earlier onset often results in a somewhat different presentation of symptoms and faster disease progression. A diagnosis of Huntington's disease is based primarily on your answers to questions, a general physical exam, a review of your family medical history, and neurological and psychiatric examinations.

Dwarfism (autosomal)

Dwarfism is short stature that results from a genetic or medical condition. Dwarfism is generally defined as an adult height of 4 feet 10 inches (147 centimeters) or less. The average adult height among people with dwarfism is 4 feet (122 cm). Many different medical conditions cause dwarfism. In general, the disorders are divided into two broad categories, disproportionate and proportionate dwarfism.

Symptoms include:

  • An average-size trunk
  • Short arms and legs, with particularly short upper arms and upper legs
  • Short fingers, often with a wide separation between the middle and ring fingers
  • Limited mobility at the elbows
  • A disproportionately large head, with a prominent forehead and a flattened bridge of the nose
  • Progressive development of bowed legs
  • Progressive development of swayed lower back
  • An adult height around 4 feet (122 cm)
  • Average age and testing:

    Your pediatrician will likely examine a number of factors to assess your child's growth and determine whether he or she has a dwarfism-related disorder. Diagnostic tests may include measurements, appearance, imaging technology, genetic tests, family history, and hormone tests.

    Down Syndrome (sex-linked)

    Down syndrome is a genetic disorder caused when abnormal cell division results in extra genetic material from chromosome 21. This genetic disorder, which varies in severity, causes lifelong intellectual disability and developmental delays, and in some people it causes health problems. Down syndrome is the most common genetic chromosomal disorder and cause of learning disabilities in children.

    Symptoms include:

  • Flattened facial features
  • Small head
  • Short neck
  • Protruding tongue
  • Upward slanting eyes, unusual for the child's ethnic group
  • Unusually shaped or small ears
  • Poor muscle tone
  • Broad, short hands with a single crease in the palm
  • Relatively short fingers and small hands and feet
  • Excessive flexibility
  • Tiny white spots on the colored part (iris) of the eye called Brushfield spots
  • Short height
  • Average age and tests:

    In 1910, a baby born with Down syndrome often didn't live to age 10. Today, someone with Down syndrome can expect to live to age 60 and beyond, depending on the severity of health problems. The American College of Obstetricians and Gynecologists recommends offering the option of screening tests and diagnostic tests for Down syndrome to all pregnant women, regardless of age.

    Cystic Fibrosis (autosomal)

    An inherited condition, cystic fibrosis affects the cells that produce mucus, sweat and digestive juices. These secreted fluids are normally thin and slippery. But in cystic fibrosis, a defective gene causes the secretions to become thick and sticky. Instead of acting as a lubricant, the secretions plug up tubes, ducts and passageways, especially in the lungs and pancreas.

    Symptoms include:

    Cystic fibrosis signs and symptoms vary, depending on the severity of the disease. In some children, symptoms begin during infancy.

    Respiratory signs are-

  • A persistent cough that produces thick spit (sputum) and mucus
  • Wheezing
  • Breathlessness
  • A decreased ability to exercise
  • Repeated lung infections
  • Inflamed nasal passages or a stuffy nose
  • Digestive signs are-

  • Foul-smelling, greasy stools
  • Poor weight gain and growth
  • Intestinal blockage, particularly in newborns (meconium ileus)
  • Severe constipation
  • Average age and tests:

    Every state in the U.S. now routinely screens newborns for cystic fibrosis. Early diagnosis means treatment can begin immediately. Cystic fibrosis tests may be recommended for older children and adults who were not checked at birth.

    All of my credit goes to:


    For most of the information that went into this project.


    For the big words and terms that I have used in this project.


    For the information specifically regarding color blindness.


    For being another source of information.


    For being a source specifically for PKU.

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