- A scientist is studying stem length in wheat plants. She crosses two highly inbred wheat strains that differ in stem height. Then selfcrosses within the F 1 generation and raises the F 2 . The average s 2 of the parentals and the F 1 = 3 , while the s 2 of the F 2 generation = 12. What is the genetic variance of population? A. 12 B. 3 C. 9 D. 15 E. We cannot tell.