ANSC 313 Lecture Notes - Lecture 22: Polycystic Kidney Disease, Heterogametic Sex, Polycystin 1
Indirect test: DNA LINKAGE TESTS!•
Used when the causative gene is not yet known!◦
Location of gene, or biochemical pathway, ect. Is known!◦
Less accurate than direct tests!◦
I.e. Depends on distance of marker to gene ( not always easy to know)!‣
use a marker linkaged to the causative gene!◦
Note: which allele segregartes with the allele of intrest is pedigree soecific!◦
Therefore must sample the family to test for carriers!◦
also used if a dominant disorder is late onset, so that the genotype us know prior to breeding!•
Example: polycystic kidney disease!•
Autosomal dominant !◦
Persian cats and breeds with persian!◦
Cysts develop by 12 months!◦
Renal failure later in life!◦
Premature stop codon in PKD1 gene!◦
Now a dna test!◦
Takes a long time for damage to accumulate till you can see damage!◦
!
Sex related inheritance patterns!
X linked!•
Y linked!•
Sex influenced!•
Sex limited!•
!
Sex linked!
Gene on the z or z chromosome!•
Due to unequal size of chromosomes!•
Heterogametic sex has fewer genes ( xy male mammal or zx female bird)!•
$ie only 1copy of several!◦
!
Therefore mammals have x- inactivation= lyonization ( after mary lyon discovered this)!
Example: sulfatase is an enzyme on the x chromosome!•
XSXS = 100% activity in female embryo!◦
XSXS= 50% activity in female!◦
Fetus/adult!‣
XSY= 50% activity in male!◦
no evidence of z inactivation in birds!•
!
Ishihara tests: colour vision test!
Usually affects males!•
Red- green color blindness is an x linked gene!•
!
X-linked traits!
Calico in cats!•
Females!◦
Xo/Xob= calico!‣
Xo/Xo= orange!‣
Xob/Xob = black!‣
males!◦
Cannot be calico!‣
Document Summary
Used when the causative gene is not yet known. Depends on distance of marker to gene ( not always easy to know) use a marker linkaged to the causative gene. Note: which allele segregartes with the allele of intrest is pedigree soeci c. Therefore must sample the family to test for carriers also used if a dominant disorder is late onset, so that the genotype us know prior to breeding. Takes a long time for damage to accumulate till you can see damage. Heterogametic sex has fewer genes ( xy male mammal or zx female bird) ie only 1copy of several. Therefore mammals have x- inactivation= lyonization ( after mary lyon discovered this) Example: sulfatase is an enzyme on the x chromosome. Xsy= 50% activity in male no evidence of z inactivation in birds. Red- green color blindness is an x linked gene.
