Genetic Disorders Genetic diseases Diseases caused by abnormalities

Genetic Disorders

Genetic diseases • Diseases caused by abnormalities in the genes or chromosomes. • Present in all body cells for the person’s entire life. • Three types: • autosomal gene diseases • sex-linked gene diseases • missing or extra chromosome diseases

Autosomal Diseases • Autosomes are all of the chromosomes except the X and Y (sex) chromosomes. • Autosomal Diseases are genetic diseases carried on autosomes. • Most Autosomal Diseases are recessive. • A person must inherit a copy of the gene from both parents to display the symptoms.

Carrier • A person is considered a carrier if they have only one copy of the defective gene. • A carrier does not have symptoms of the disease. • A carrier can pass the defective gene to their children.

Cystic Fibrosis • Autosomal recessive disorder • 5% of population carries the gene for cystic fibrosis found on chromosome 7. • Affects all ethnic groups. • Creates a protein that makes an affected person’s body produce abnormally sticky, thick mucus. • No cure • Some CF babies die in infancy. Others live into their 20’s or 30’s.

Cystic Fibrosis • Symptoms and Effects: • severe lung infections • prevents pancreatic enzymes from breaking down food and absorbing nutrients • persistent cough, wheezing, or shortness of breath • poor growth • excessive appetite with weight loss • greasy, bulky stools

CF Diagnosis and Treatment • Since CF patients sweat is extremely salty, people are diagnosed with CF using a test that measures the amount of salt in a person’s sweat. • High salt levels indicate cystic fibrosis. • Treatments include: • airway clearance techniques ( postural drainage and percussion) • breathing treatments to loosen the mucus. • Lung transplants may ultimately be required.

Phenylketonuria • Autosomal recessive disorder • known as PKU • Missing the enzyme phenylalanine hydroxylase that breaks down phenylalanine and allows the body to use it. • phenylalanine is one of the eight essential amino acids found in protein. • Phenylalanine builds up in the body and affects the central nervous system and causes brain damage.

PKU Diagnosis and treatments • PKU is diagnosed easily by a blood test and every newborn baby in the US is tested shortly after birth. • PKU can be treated by following a strict diet avoiding proteins that contain phenylalanine until age 5 or 6. • If a strict diet is not followed during infancy and early childhood the child will develop: • severe mental retardation by age one • tremors • seizures • hyperactivity

TAY-SACHS • Autosomal recessive genetic disorder • Eastern European Jewish descent most often affected (VERY RARE) • Babies appear normal for the first few months of their lives then fatty material begins building up in their nerve cells and brain. • Babies progressively lose motor skills. Children become deaf, blind, and unable to swallow. • Eventually paralysis sets in. • Children rarely live past age four, some live until 6. • No Cure. • Only treatment is for symptoms and comfort.

Cherry Red Spot • Identifying characteristic of Tay-Sachs • The center of the fovea in the back of the eye appears bright red and is surrounded by a milky halo

Autosomal Dominant Disease • Only one defective gene has to be present for a person to have the disease. • The dominant defective gene is expressed over the normal gene. • If a parent is affected then there is a 50% chance they will pass the defective gene to their offspring.

Huntington’s Disease • Autosomal dominant disease • More than 15, 000 Americans have HD. At least 150, 000 others have a 50% risk of developing the disease. • HD is a progressive disease in which symptoms typically develop during a person’s 30’s or 40’s (could be earlier or later). • HD results from a degeneration of nerve cells (neurons) in certain areas of the brain. This causes uncontrolled movements, loss of intellectual faculties, and emotional disturbance. It also affects the brain’s outer surface (cortex) which controls thought, perception, and memory.

Huntington’s Disease • The disease can reach the point where speech is slurred and vital functions (swallowing, eating, speaking, walking) decline. • Some patients can not recognize their family members. • Many remain aware of their environment and are able to express emotions.

Sex-Linked Disease

Hemophilia • Sex-Linked Genetic Disease • Gene for Hemophilia A or B is located on the X chromosome. • Can NOT be passed from father to son. • Almost always occur in boys and is passed from mother to son. • Women are carriers of the defective gene and have no symptoms. • Hemophilia C can be passed on to children by either parent. • Hemophilia C occurs in both boys and girls • milder than Hemophilia A or B

Color Deficiency • Carried on the X chromosome • Passed from mother to son most often.

Missing or Extra Chromosomes • Occurs during meiosis • Passed on to offspring • Present in every cell of the affected offspring

Down’s Syndrome • Trisomy 21 (extra chromosome at the 21 spot) • Caused by nondisjunction during meiosis. • One of the most common genetic birth defects • Results in a combination of birth defects including: • mental retardation • characteristic facial structures • heart defects • visual and hearing impairment

Turner Syndrome • Females missing one or part of one of their X chromosomes • Results from nondisjunction during meiosis • Effects vary widely depending on the number of cells affected by the changes to the X chromosome. • Causes growth problems, underdeveloped ovaries (sterility and hormone related issues), kidney problems, high blood pressure, heart problems, overweight, hearing difficulties, diabetes, thyroid problems, and some learning difficulties

Characteristics • A "webbed" neck (extra folds of skin extending from the tops of the shoulders to the sides of the neck) • A low hairline at the back of the neck • Drooping of the eyelids • Differently shaped ears that are set lower on the sides of the head than usual • Abnormal bone development (especially the bones of the hands and elbows) • A larger than usual number of moles on the skin • Edema or extra fluid in the hands and feet