Hemophilia is an X-linked recessive disorder that is passed through generations and can be traced by using a pedigree. Ann and Marie are half-filled circles. Fred and Luke are filled squares. Who has hemophilia in the pedigree that is shown? John and Ann Fred and Luke John, Charles, Jack, and Irene Ann and Marie.

Amylase is an enzyme found in the human digestive system. why do you think it was important to keep the enzyme temperature about 37 degrees celsius (98.6 degrees f)? describe what might happened the temperature decreased by 10 degrees celsius.

To answer this question, researchers studied populations of the dusky salamander (desmognathus ochrophaeus) living on different mountain ranges in the southern appalachian mountains. the researchers tested the reproductive isolation of pairs of salamander populations by leaving one male and one female together and later checking the females for the presence of sperm. four mating combinations were tested for each pair of populations (a and b)—two within the same population (female a with male a and female b with male b) and two between populations (female a with male b and female b with male a). the proportion of successful matings for each mating combination was measured. for example, when all the matings of a particular combination were successful, the researchers gave it a value of 1; when none of the matings were successful, they gave it a value of 0. then the researchers calculated an index of reproductive isolation that ranged from 0 (no isolation) to 2 (full isolation). the reproductive isolation value for two populations is the sum of the proportion of successful matings of each type within populations (aa + bb) minus the sum of the proportion of successful matings of each type between populations (ab + ba). the table provides data for the geographic distances and reproductive isolation values for 27 pairs of dusky salamander populations.

Crossing over and independent assortment are important activities that occur during meiosis. what is the significance of these activities