identical twins

[Peter Gooding]

ggutman at MEDED.MED.UCI.EDU (George Gutman) wrote:
>"Siblings" refers to offspring of the *same* parents, not just 
>genetically identical parents.  The offspring of different mating pairs 
>of inbred mice, for example, are not siblings, despite the fact that they 
>are genetically identical to each other (as well as to their parents, and 
>all other members of the same inbred strain).  So the human offspring in 
>question are certainly not "siblings".

This depends on your definition of "*same* parents". 
How do you know that the parents arent the "same", when we are talking about genetics?
If we are talking about genetics, then the parent pairs are genetically the same, and
the offspring are genetic siblings, even if they aren't genealogical siblings.

If two individuals (ie the mice) are genetically identically because they are 
selectively bred from the same ancestoral stock, or a rare occurance of identical 
recombination of chromosomes, and have different parents, this is a different 
situation entirely from being sourced from an identical genetic cross.

If,however,you refer to "they" as your so described "different mating pairs" being 
identical genetic crosses then you certainly must explain their origin, particularly 
as you now require *two* pairs of genetically identical individuals who are not 
related as twins or siblings, to describe a more generalised example of identical 
genetic crosses which would prove the two twins case.

And so, how can you clarify the genealogical relationship between an inbred strain of 
mice, when for example a mouse's parent may also be its grandparent, half-sibling, 
aunt, two of its grandparents, great-grandparent, a cousin, etc. ? 

Peter Gooding


-Not qualified in Biology.