Download Human X-linked Recessive Disorders 1. Hemophilia What is

Human X-linked Recessive Disorders
1. Hemophilia
What is hemophilia? What causes hemophilia?
 blood disorder in which blood does not clot properly
 bleeding can be external or internal
 several proteins are involved in the blood clotting process (clotting factors 1
through 13)
 in the most common form of hemophilia (Hemophilia A), the protein known as
Factor VIII is missing or defective
 in a less common form of hemophilia (Hemophilia B), the protein Factor IX is
missing or defective
How common is hemophilia?
 hemophilia is more likely to be found in men and rarely found in women; however
women can be gene carriers of the disease
 in the United States, about 20,000 males have hemophilia
 about 90 percent of those with hemophilia have type A
 among U.S.-born males, about one in 5,000 will have hemophilia
What are the symptoms of hemophilia?
 individuals bleed longer and more profusely from sustained injuries
 frequent and hard-to-stop nosebleeds
 internal bleeding from the joints and muscles which can results in organ damage
 blood sometimes observed in stool or urine
 if there is bleeding in the joints, joints become tight, swollen, painful, and warm to
the touch
 bleeding in the brain may cause long headaches, neck stiffness, vomiting,
sleepiness, behavior changes, double vision, convulsions, seizures, weakness in
arms or legs, difficulty walking
What are the available treatments?
 with proper treatments, these individuals lead very normal lives
 “replacement therapy” performed which involves infusing a clotting factor into the
bloodstream
 depending on severity of the case, some individuals receive regular infusions,
while others only receive infusions on an as-needed basis
 both approaches can be performed at home
2. Color Blindness
What is color blindness? What causes color blindness?
 color vision deficiency, characterized by a person’s inability to differentiate
between various colors
 in most cases, the individual is lacking or deficient of cone receptor cells in the
retina, usually either green cones or red cones
How common is color blindness?
 ~ 8% of all men and 0.5% of all women suffer from color blindness
 approximately 95-99 percent of all color blind people suffer from red-green color
blindness
 around 75 percent of people suffering from red-green color blindness lack or are
deficient of green cones, while the remaining 24 percent lack or are deficient of
red cones
 blue cone deficiencies are very rare and are NOT sex-linked (chromosome 7)
 tends to be a bit more prevalent in Caucasian population than any other group
What are the symptoms of color blindness?
 Confusion between reds and greens
 However, the problem prevails in the whole color spectrum