Wednesday, 25 January 2012

Solving Pedigrees - Now testing for X-linkage!

Here are those same two pesky pedigrees from before.  In the previous post you had a chance to determine whether the mutant allele was dominant or recessive to wild-type.
 The one above MUST be recessive because two unaffected parents produced affected children.  Now try it with X-linkage.  You can use the symbols Xr and XR to denote a recessive mutant allele and the dominant wild-type allele, respectively.  Here's a solution:

And as for this one, we can't rule out dominant so easily!  Check this for both an X-linked recessive and an X-linked dominant pattern of inheritance.  The solution is below.

Tuesday, 17 January 2012

Solving pedigrees

Here's a good warm-up exercise.  You should be able to determine all possible inheritance patterns for these pedigrees.  For now, ignore whether they are autosomal or sex-linked.  Determine whether the inheritance is consistent with a dominant or a recessive allele.  You may assume that there is a simple Mendelian interaction here:  the allele that causes the special phenotype (shaded symbols) is either completely recessive or completely dominant to the wild-type (unfilled symbols).

Pedigree 1:

Solution for the pedigree above.  (Click on the YouTube logo at the bottom right if you want to be able to open a full-screen version).

Pedigree 2:

The solution for Pedigree 2 is below (same notation regarding full-screen view).

Determining Parental Genotypes from Offspring Ratios

Here is an exercise that calls for figuring out the genotypes of parents based on the ratios of their offspring.  Here are the data:

The solution can be found below.  If you want to make it full size, you should click on the YouTube logo on the bottom right corner of the embedded file, then you can zoom it.  (Blogspot doesn't zoom).