Human Genetic Disorders Every cell in the human body has 46 chromosomes except for gametes, egg sperm cells, which contain 23 or the haploid number. Human genetic disorders can result from the inheritance of a single gene, or an entire chromosome.

Autosomal disorders The following diseases are known as autosomal, because their inheritance is based on a single gene, dominant or recessive, and is not linked to the sex of the individual.

Albinism *Absence of skin pigment, sensitive to light, need to avoid sunlight * 1 in 17,000 in US * Recessive trait * Visual impairment * Diagnosis made by blood test

Cystic Fibrosis Second most common childhood onset disorder in US 1 in 3,200 whites, 1 in 14,000 African Americans Recessive trait Mucus builds up in respiratory tract Treatment includes antibiotics, breathing treatments Mothers can be pre-screened prior to birth. Sweat test used in older patients Survival rates have risen to average of 33 years of age

Huntington’s Disease Autosomal dominant Symptoms develop between years of age Lack of concentration, loss of muscle control, clumsiness No treatment exists, death is certain 1 in 10,000 Americans Gene testing done to diagnose May consider genetic counseling if it runs in the family

PKU (Phenylketonuria) Recessive trait Inability to utilize phenylalanine, an enzyme 1 in 10,000 births Diagnosed at birth with blood test Treated with diet to avoid phenylalanine Mental retardation may result without treatment

Polycystic Kidney Disease 1 in 500,000 in US Dominant trait May live for decades without symptoms Urinary tract infections, high blood pressure, kidney stones, enlarged kidneys Diagnosed by family history and ultrasound Treatment is dialysis and kidney transplant

Tay Sachs Recessive trait Carried by 1 in 30 Jewish Americans Fatal disease Healthy at birth, quickly develop symptoms, nervous system breaks down Death by age 5

Sex-linked traits Sex-linked traits are those that are linked or occur on the X chromosome. Since females are XX and males are XY, the male need only inherit one gene for the trait in order to have the trait. This is why these disorders are more common in males and rare in females

Muscular Dystrophy Sex-linked, recessive disease More common in males On set varies Life expectancy varies Causes muscle weakness, loss of mobility, speech Diagnosed by blood test Treatment involves crutches, wheelchairs, orthotics, possibly surgery Occurs in 1 in 3,500 males

Color blindness Sex-linked recessive 1 in 12 men, 1 in 200 women Severity of colorblindness varies No treatment Diagnosed with color blot tests

Hemophilia Sex-linked recessive Results in the lack of clotting factor in the blood Diagnosed by blood test, genetic screening Treated by blood transfusions 1 in 7,500 males 1 in 25,000,000 females!

Chromsomal Disorders In some cases, an entire chromosome can be missing, or there can be an extra chromosome. These types of disorders usually result in more severe defects.

Human Karotyping Human chromosomal disorders can be diagnosed through a karyotype. This involves removing amniotic cells from the mother, taking an x-ray of the chromosomes, cutting them out an counting them up. If the number of chromosomes is not 46, there is a chromosomal defect

Down Syndrome Result of an extra 21st chromosome (trisomy 21), random 1in 700 births Wide range of symptoms Slower developmental process, some learning impairment Physical features, shape of face, eyes Life expectancy years

Edward syndrome Trisomy 18- extra 18th chromosome, random 50% of babies die by one week of age Growth deficiency, feeding and breathing difficulty, mental retardation Can be detected by amniocentesis No treatment 1 in 6,000 live births many fetuses self-terminate

Sex Chromosomal Disorders A handful of chromosomal disorders occur involving the sex chromosomes. Since a normal female is XX and a normal male is XY, inheriting an extra sex chromosome, or missing one can have effects upon the sexual development of individuals

Turner Syndrome Occurs when an X chromosome is damaged or missing (X_) Diagnosed with a karyotype Occurs in 1 of 2,500 females Treatment involves hormone therapy Females may be of short stature and have delayed puberty if untreated Random inheritance

Klinefelter Syndrome Caused by the inheritance of an extra X chromosome by a male (XXY) Results in breast development, sparse facial hair, inability to produce sperm Occurs in 1 in 1,000 male births Treatment may include testosterone injections Diagnosed prior to birth by amniocentesis Random inheritance

Trisomy X Effects females who inherit 3 x chromosomes (XXX) Occurs 1 in every 1,500 births Many have no symptoms Diagnosed by amniocentesis May have infertility, tall stature, increased space between eyes Random inheritance