X-LINKED DISEASES

Question 1

random inactivation of either paternally or maternally inherited X-chromosome
occurs in each cell of females

Answer 1

Lyon Hypothesis

Question 2

X-linked Dominant Disorder

mental retardation, infertile females, prenatally lethal in males

Answer 2

Rett Syndrome

Question 3

X-linked Dominant Disorder

normal production/metabolism of vitamin D

Renal tubular loss of phosphate – interferes w/ skeletal ossification

Answer 3

Vitamin D Resistant Rickets

Question 4

X-linked Recessive Disorder

complete lack of HGPRT

Clinical Signs – normally in constraining wheelchair
▪ Appears normal at birth, and develop normal for months
▪ High uric acid levels
▪ Self-mutilation
▪ Mental retardation & spasticity
▪ Profound lack of dopaminergic terminals and cells
▪ Gout

Answer 4

Lesch-Nyhan Syndrome

Question 5

OTHER TYPES OF INHERITANCE

combined actions of environment and two or more mutant genes

Answer 5

Multifactorial Inheritance

Question 6

OTHER TYPES OF INHERITANCE

Characteristics?

Answer 6

• risk for disorder is influenced by # of mutant genes inherited
• rate of recurrence is same for all 1st degree relatives
• risk of both identical twins getting disorder is <100%

Question 7

OTHER TYPES OF INHERITANCE

Examples?

Answer 7

o Congenital heart disease
o DM
o Cleft lip/palate
o Hypertension
o Gout