Lecture 14 Flashcards
What does it mean to be hemizygous?
Males; only have one copy of the X chromosome
What are the X-linked recessive disorders?
- duchenne muscular dystrophy (severe)
- becker muscular dystrophy (mild)
- Glucose 6-phosphate dehydrogenase deficiency
- hemophilia A and B
- lesch-Nyhan syndrome
- red-green color blindness
- X-linked SCID
Dystrophin associated muscular dystrophy
Beckers muscular dystrophy (mild)
Duchennes muscular dystrophy (severe)
Due to a DMD mutation
x-linked recessive
Glucose 6-phosphate dehydrogenase (G6PD) deficiency
hemolytic anemia on ingestion of primaquine, sulfa drugs
x-linked recessive
Hemophilia A and B
Bleeding tendencies
x-linked recessive
Lesch-Nyhan syndrome
HGPRT deficiency
causes hyperuricemia, gout, & self mutilation
x-linked recessive
Red-green color blindness
x-linked recessive
X-linked SCID
x-linked recessive
defect in the SCIDX1 gene
Y-linked inheritance
only males
mutations usually lead to infertility
Examples of Y-linked inheritance
Various mutations in the SRY genes
H-Y histocompatibility antigen
Hairy ears
Osteogenesis imperfecta:
A defect in collagen
mutation on chromosome 17 (COL1A1) or 7 (COL1A2)
locus heterogeneity
Disorder that show locus heterogeneity?
- Sensorineural hearing impairment (many types)
- Retinitis pigmentosa
- Charcot Marie Tooth disease (AD, AR, or X-linked)
- SCID (AR and X-linked)
- osteogenesis imperfecta
What are the three reasons for variable expression?
- random chance
- other genetic factors (modifier loci) or sex influence
- environmental exposure
Hemochromatosis
is an iron overload disorder (autosomal recessive disorder)
worse in males than females
variable expression due to gender
Xeroderma pigmentosum
autosomal recessive
more severe in individuals exposed more frequently to
environmental UV radiation
first child vs second child (variable expression)
