Re: What determines jumping genes to jump to new locations on a chromosome?

Jumping genes are genetic elements which are called Transposons or 
Transposable element (sometimes they are also called Insertion Elements or 
Insertion Sequences). These terms all mean the same thing and 
refer to segments of DNA which can move from one location on a chromosome 
to another location, or to another chromosome.

Where do they jump to? That really depends upon the element itself and 
whether it has any specificity for a target sequence. These elements use 
proteins to make a cut in the DNA into which they can insert or replicate 
themselves. Sometimes this cut is random and can occur almost anywhere, 
other proteins are more specific and only make cuts at certain DNA 
sequences. But most elements can jump to lots and lots of different 
locations. Sometimes these are in junk regions between genes, other times 
they insert into genes themselves and cause mutations. In fact their 
ability to cause mutations is how they were discovered.  

Generally these elements are only thought to move around within a cell, in 
other words they move around the chromosome, but they generally do not 
between organisms (except of course they are inherited from parents to 
children). However if one organism died and its DNA was taken up by a 
scavenger organism, then it might be possible for the element to jump into 
this new organism (if they were similar enough). However this happens very 
very rarely, but it likely has happened a few times in evolutionary 
history. We know this because we can occasionally find very similar 
elements in different species, which is unusual.

But most transposable elements are very species specific and don't tend to 
move around.