A yeast strain that cannot grow in the absence of the amino acid histidine (his-) is mated with a yeast strain that cannot grow in the absence of the amino acid lysine (lys-). Among the 400 unordered tetrads resulting from this mating, 233 were PD, 11 were NPD, and 156 were TT. a. What haplotypes of spores are in the PD, NPD, and TT tetrads? (10 pts.) b. What is the distance in map units between the his and lys genes? (10 pts.) c. Assuming that none of these tetrads was caused by more than two crossovers between the genes, how can you estimate the number of meioses that generated these 400 tetrads in which zero, one, or two crossovers took place? Estimate the number.

Hormones are chemical molecules produced by endocrine glands. one such endocrine gland is the thyroid gland, which synthesizes the thyroid hormone, which in turn affects the heart muscles. which two statements describe the probable reason for the function of the hormone? the cells in the heart have specific receptors that allow for the intake of hormones. the heart and the endocrine glands have the exact same types of cells. all cells make the same types of hormones. thyroid hormones show their effect on the heart by means of specialized cells. thyroid cells and cardiac cells have different dna.

Monarch butterflies have brightly colored orange wings with black patterns on them, making them easily visible to birds that eat butterflies and moths, yet birds rarely eat the monarchs. likewise, the monarch caterpillars are brightly striped yellow and white and black, and they also are rarely eaten by birds, although some wasps will attack them and feed them to their young. what can be inferred from these observations? monarchs must threaten and attack birds, but not wasps. monarchs have a way of discouraging bird predation that does not involve hiding. monarchs’ wings are so colorful that most birds must find them difficult to eat. monarchs lay more eggs than other less conspicuous butterflies.

How many pounds does the earth weigh?