9 22 Genetics Consiguity-Table 1 Flashcards
when does inactivation occur in the cells of a female?
at about the 10-20 cell stage
why would a female manafest an x-linked recesive disease?
they may have enough of the normal x chromosome inactivated to make it not a clear 50 50 split and they may express some of the disease traits
how do we estimate the allele frequency (gene frequency) for x-linked recessive disease?
take the prevalence in males, and this is equal to the allele frequency (q).
how do we find the frequency of a x-linked disease in females?
predict the gene frequency (q) using the prevelence in males and then for females use q*q or the prevelence squared.
what causes hemophelia?
factor VIII deficiency: hemophilia A; factor IX deficiency: hemophilia B
why would a father never pass red-green colorblindness onto a son?
it is an x-linked recessive trait.
what is the phenotype for hemophilia A?
clotting time is increased; bruising, hemorrhage; hemarthrosis (bleeding into the joints)
how could we genetically treat hemophelia?
AAV vecotor injected into peripheral vein to activate factor gene activity
what is Duchenne muscular dystrophy?
it is the most common form of muscular dystrophy and one of the most deadly form of muscluar dystrophy – due to lack of dystrophin to connect the actin fibers to the intermembrane components and to the components outside of the cell.
what are some early signs of duchenne muscular dystrophy?
gowers sign (climb up the legs to stand up); proximal wasting pseudohypertrophy of the muscles.
what are some late stage signs of duchenne?
severe muscle wastage, elevated creatine kinase; invovlement of cardiac and respiraotory muscles, decreased average IQ
what are two experimental therapies for Duchenne?
ribosomal readthrough with PTC124 skips the premature stop codon. 2. Exon skipping
what is the genetic cause of duchenne?
2/3 of the mutations in DMD gene are deletions or insertions that cause frame shift mutations.
what would occur if you have a dystrophin altered by a reading frame instead of deleted by a non-sense mutation like DMD
You would get Becker muscular dystrophy, which is a slower form of the disease.
what identifies a pedigree as X-linked dominant?
male-male transmission is not seen; heterozygous females are affected; affected females seen twice as often as affected males, on average; disease phenotype seen in multiple generations; skipped generations unusual.
