Hi
Suppose a population of animals (say, a herd of sheeps). They have a specific number of chromosomes.
Now suppose that a baby is born in this herd with a different number of chromosomes. When this baby grows up, he/she will marry someone else in the herd. Since this couple have different number of chromosomes, can it be possoble for them to reporulate?

Thank you.

Each species has a specific number of chromosomes and that number doesn't change except in the case of disease. Animals of two different species are unable to produce fertile offspring

correct and just to add that in the event in a specific individual if a chromosomal rearrangement or fusion occurred in most cases that would result in a non-viable foetus. In the event that a chromosomal fusion had no deleterious effects then that animal might be fertile and thus able to pass on that new chromosomal number to the next generation. that for example is thought to have happened in primates o humans - see below.
http://www.askabiologist.org.uk/answers … hp?id=1048

Actually... I'm not sure if the above is entirely true!

Karyotypic studies ( = studies of the number and arrangement of chromosomes) from the 60's and 70's are rife with reports of within-species variation in chromosome number. From memory this is true in both plants and animals - for instance, in Atlantic salmon chromosome numbers of 53-60 have been reported accoding to the paper here. I think in most cases variation in chromosome number is more pronounced between populations (rather than among individuals within a population) but I could be wrong.


http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2995484/

I was thinking more about humans with translocations or fusions, not all of which are deleterious. Thus fusion of 2 chromosomes might rarely be stable and balanced and thus could be passed on to future generations.

That makes sense. I may be wrong but my memory of the chromosomal variation in salmon (and I think other salmonids) is that chromosome "arm" number is quite stable, but there can be more or fewer acrocentric chromosomes.