$\text{\blue{WHAT IF?}}$ A rooster with gray feathers and a hen of the same phenotype produce $15$ grays, $6$ black, and $8$ white chicks. What is the simplest explanation for the inheritance of these colors in chickens? What phenotypes would you expect in the offspring of a cross between a gray rooster and a black hen?

A man has six fingers on each hand and six toes on each foot. His wife and their daughter have the normal number of digits. Remember that extra digits is a dominant trait. What fraction of this couple’s children would be expected to have extra digits?

Suppose at the end of a hard run on a hot day you find that there are no drinks left in the cooler. If, out of desperation, you dunk your head into the cooler, how might the ice-cold water affect the rate at which your body temperature returns to normal?

Fusicoccin is a fungal toxin that stimulates the plasma membrane H$^+$ pumps of plant cells. How may it affect the growth of isolated stem sections?

Three characters (flower color, seed color, and pod shape) are considered in a cross between two pea plants: PpYyIi x ppYyii. What fraction of offspring are predicted to be homozygous recessive for at least two of the three characters?

You can see that the skin-color phenotypes are not distributed uniformly.

Distributions of values like this one tend to show one of several common patterns. Sketch a rough curve that approximates the values and look at its shape. Is it symmetrically distributed around a central peak value (a "normal distribution," sometimes called a bell curve); is it skewed to one end of the x-axis or the other (a "skewed distribution"); or does it show two apparent groups of frequencies (a "bimodal distribution")? Explain the reason for the curve's shape.

You can see that the skin-color phenotypes are not distributed uniformly. (a) Which phenotype has the highest frequency? Draw a vertical dashed line through that bar. (b) Distributions of values like this one tend to show one of several common patterns. Sketch a rough curve that approximates the values and look at its shape. Is it symmetrically distributed around a central peak value (a "normal distribution," sometimes called a bell curve); is it skewed to one end of the $x$-axis or the other ( $a^n$ skewed distribution"); or does it show two apparent groups of frequencies (a "bimodal distribution")? Explain the reason for the curve's shape. (It will help to read the text description that supports Figure $14.13.$)

Explain how the change of a single amino acid in hemoglobin leads to the aggregation of hemoglobin into long fibers.

The pathogenic fungus Fusicoccum amygdali secretes a toxin called fusicoccin that activates the plasma membrane proton pumps of plant cells and leads to uncontrolled water loss. Suggest a mechanism by which the activation of proton pumps could lead to severe wilting.

Suppose an Arabidopsis mutant lacking functional aquaporin proteins has a root mass three times greater than that of wild-type plants. Suggest an explanation.

If a man with type AB blood marries a woman with type O, what blood types would you expect in their children? What fraction would you expect of each type?

Two organisms, with genotypes BbDD and BBDd, are mated. Assuming independent assortment of the B/b and D/d genes, write the genotypes of all possible offspring from this cross and use the rules of probability to calculate the chance of each genotype occurring.

A man with type A blood marries a woman with type B blood. Their child has type O blood. What are the genotypes of these three individuals? What genotypes, and in what frequencies, would you expect in future offspring from this marriage?

List all gametes that could be made by a pea plant heterozygous for seed color, seed shape, and pod shape (YyRrIi). How large a Punnett square would you need to draw to predict the offspring of a self-pollination of this “trihybrid”?