<span>If each of the pairs of
chromosomes was heterozygous (what gives you the highest potential
number of different gametes), then the number of possible gametes
increases from 4 to 8 for a diploid organism. To figure out how many
are possible, raise the number of homologous chromsomes (2 for a diploid
organism) to the power of the number of chromosomes. So if you have
two different chromosomes (A and B), raise 2 to the 2nd power (or
multiply 2 x 2) and you have 4. If you have chromosomes A, B, and C,
then you have 2^3, or 2 x 2 x 2 = 8.
To show possible combinations, AaBb gives you AB, Ab, aB, or ab. AaBbCc
gives possible gametes of ABC, ABc, AbC, Abc, aBC, aBc, abC, and abc. </span>
I think that the best phrase to fit into the blank is a "scientific theory".
A scientific theory is developed through experiments which use the scientific method, and a theory can be improved if additional data is available or if people provide suggestions which make the theory fit the data better.
