Chapter 5, Problem 15P

Three dominant traits of corn seedlings, tunicate seed( $\text{T–}$), glossy appearance ( $\text{G–}$), and liguled stem ( $\text{L–}$), arestudied along with their recessive counterparts, nontunicate ( $\text{tt}$), nonglossy ( $\text{gg}$), and liguleless( $\text{ll}$). A trihybrid plantwith the three dominant traits is crossed to a nontunicate, nonglossy, liguleless plant. Kernels on ears of progenyplants are scored for the traits, with the following results:

$\begin{array}{cc}Phenotype& Number\\ Tunicate,glossy,liguled& 102\\ Tunicate,glossy,liguleless& 106\\ Tunicate,nonglossy,liguled& 18\\ Tunicate,nonglossy,liguleless& 20\\ Nontunicate,glossy,liguled& 22\\ Nontunicate,glossy,liguleless& 23\\ Nontunicate,nonglossy,liguled& 99\\ Nontunicate,nonglossy,liguleless& 110\\ & 500\end{array}$

a. Is there evidence of genetic linkage among any of thesegene pairs? If so, identify the evidence.

b. Is there evidence of independent assortment among any of these gene pairs? If so, identify the evidence.

c. Using the gene symbols given above, write the genotypes of $\text{F1}$ and $\text{F2}$ plants.

d. If evidence of linkage is present, calculate the recombination fraction(s) from the data presented.

e. Could all three genes be carried on the same chromosome? Discuss why or why not.