What are the physical effects of a balanced Robertsonian Translocation of
Chromsome 22 in humans?  There is allegedly no genetic material
missing and no extra material present.

Hope this helps, but I fear it won't.

"An association between DiGeorge's syndrome and an unbalanced
chromosomal rearrangement leading to trisomy 20pterrarr20q11 and
monosomy 22pterrarr22q11 was found in four individuals belonging to
one family. These and other data from the literature are interpreted
to suggest that DiGeorge's syndrome can be caused by deletion of a
gene located in chromosome 22, probably in band 22q11."

Balanced translocations (where no genetic material is missing) often
have no effect on the carrier.  When they do, it is when the breakage
occurs in the middle of a gene (including its control region).

However, there is potentially a serious effect on the children of an
individual with a balanced translocation.

Here's why:  Normal people have 2 copies of each chromosome (and
therefore 2 copies of each gene).  You need both copies to be normal,
by and large.  In a translocation, some genetic material is moved from
one chromosome to another.  (Robertsonian translocations are a
particular type of this, but that is unimportant to this discussion).

Now, when you form a gamete (sperm or ovum), you take one copy of each
gene.  Let us say that in this case, part (the long arm) of one copy
of chromosome 21 has been moved to one copy of chromosome 22.  All
other chromosomes are normal, and we will ignore them.  So we have one
normal copy of chromosome 21 and of chromosome 22, and one copy of
chromosome 21 missing some material, and one copy of chromosome 22
that has gained some material.  There is an equal chance of an
abnormal or a normal chromosome being selected for a particular
gamete.  So 1 in 4 gametes will be normal (and therefore will produce
a normal child).  The others will either have an extra copy of the
part of chromosome 21 (which will produce a child with Down's
syndrome), or will be missing this piece (which will produce a
miscarriage).

Cheers