Researchers have crossed two true-breeding lines of peas that differ in the color of their leaf tissue: dark green vs pale green. After selfing the resulting F1s to produce an F2 population, they characterized the phenotypes for 200 F2 individuals and report 122 dark and 78 pale plants. You want to test the for the possibility that the dark phenotype is determined by a dominant allele at a single locus. Using that as your null hypothesis, how many of the 200 F2 individuals would you have expected to be dark

150 individuals

Explanation:

If the dark phenotype is determined by a dominant allele at a single locus, the ratio of dark green phenotype to pale green phenotype at F2 should be 3:1 according to the Mendelian standard.

200 to 3:1 = 150:50

Hence, if 200 F2 individuals were characterized, one would expect the number of dark green individuals to be 150 while the pale green would be expected to be 50.

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.