The Following Table Shows Several Bacterial Strain Lac Operon Genotypes

The following table shows several bacterial strain lac operon genotypes (some are partial diploids).
a. Fill in the blanks in the "lactose absent" and "lactose present" columns in this table. (+) means significant levels of active ß-galactosidase enzyme can be detected. (-) means no significant levels of active ß-galactosidase enzyme are present. The first line is filled in for reference.

$\begin{array}{|l|c|c|}\hline\text { Strain genotype }&\text { Lactose absent } & \text { Lactose present } \\\hline 1. l a c I^{+} l a c P^{+} l a c O^{+} l a c Z^{+} l a c Y^{+} &-&+\\\hline \text { 2. } \operatorname{lacI}^{+} \operatorname{lac}^{+} \operatorname{lac} O^{+} \operatorname{lacZ^{+}} \operatorname{lac} Y^{+}\\\hline 3. l a c I^{+} l a c P^{+} \operatorname{lac} O^{+} \operatorname{lacZ^{-}lacY^{+}} \\4. l a c \mathrm{l}^{*} l a c P^{+} \operatorname{lac} O^{+} \operatorname{lacZ}^{+} l a c \mathrm{Y}^{+} \\\text { 5. } \operatorname{lacI}^{-} \operatorname{lacP^{+}} \operatorname{lacO^{+}\operatorname {lac}Z^{+}lacY^{+}/lacI^{+}}\\\text { 6. } \operatorname{lac} I^{\top} \operatorname{lacP^{+}} \operatorname{lac} O^{+} \operatorname{lacZ^{+}} \operatorname{lac} Y^{+} / \operatorname{lac} I^{+}\\\hline\end{array}$
b. Using your answers in the previous table, explain the dominance relationships among the three lacI alleles (lacI⁺, lacI⁻, lacI^s).