2. In dogs, there is an hereditary deafness caused by a recessive gene, "d." A kennel
owner has a male dog that she wants to use for breeding purposes if possible. The dog
can hear, so the owner knows his genotype is either DD or Dd. If the dog's genotype is
Dd, the owner does not wish to use him for breeding so that the deafness gene will not
be passed on. This can be tested by breeding the dog to a deaf female (dd). Draw the
Punnett squares to illustrate these two possible crosses. In each case, what
percentage/how many of the offspring would be expected to be hearing? deaf? How
could you tell the genotype of this male dog? Also, using Punnett square(s), show how
two hearing dogs could produce deaf offspring.

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.

16. which of the following accurately describes a step within transcription? a. dna polymerase uses one strand of rna as a template to put together nucleotides. b. the dna strand is used as a template for which a complementary rna strand can be produced. c. the rna strand forms a template by which dna can be built. d. the rna strand is produced within the cytoplasm.

18. how do the cells in meiosis differ from the cells in mitosis?