For a mono•hybrid cross, this is the number of rows or the number of columns in a Punnett square.
Under a molecular clock, the "snowball effect" dictates that the number of incompatibilities scales with at least this power of time since divergence. For haploid species, this constant times the effective population size gives the expected time to coalescence. In the Dobzhansky-Muller model, this is the minimum number of different loci needed for hybrid incompatibility. The coefficient of relationship through a given path is equal to one over this constant to the power of the number of (*) generations of separation. Crossing organisms that are themselves the results of crosses between genetically distinct individuals yields a hybrid generation denoted by "F" and this number; for a Mendelian trait, that generation has a three-to-one pheno•type ratio. For a mono•hybrid cross, this is the number of rows or the number of columns in a Punnett square. For 10 points, give the number of distinct sex chromosomes in humans.
Under a molecular clock, the "snowball effect" dictates that the number of incompatibilities scales with at least this power of time since divergence.
two [or second] &lt;Kothari&gt;