256 ❯ STEP 4. Review the Knowledge You Need to Score High
❯ Answers and Explanations
- B—The water will flow into the dialysis bag
because the solute concentration in the bag is
higher than that of the beaker. This creates an
osmotic driving force that moves water into the
bag in an effort to equalize the discrepancy in
solute concentrations. - D—The rate of reaction can be approximated by
calculating the slope of the straight portion of
the graph. In this case it is 15 μmol of product
produced in 5 minutes for an approximate rate
of 3 μmoles/min. - A—The distance between the gene and the cen-
tromere in Sordariais determined by adding up
the number of crossovers that occur and dividing
that by the number of offspring produced. This
quotient should be multiplied by 100, and that
product represents the percent of the offspring
that experienced crossover. This percentage
should be divided by 2 to obtain the distance
from the centromere to the gene of interest. - C—The factors that increase the rate of transpi-
ration are high light intensity, high temperature,
low humidity, and high airflow. - D—The more current you put through the gel,
the faster the DNA will migrate. Adding more
DNA will result in thicker bands. Reversing the
positive and negative ends will swap the direc-
tion in which the DNA migrates. Running the
gel for a longer amount of time will increase the
distance that the DNA fragments travel, and
increasing the temperature really won’t have too
much of an effect.- B—This is an example of genetic drift, in which
a random chunk of the population is eliminated
resulting in a potential change in the frequencies
of the alleles being studied. - C—If you allow only the plants with the dark-
pink flower genes to reproduce, those are the
genes that will be passed on to the next genera-
tion. This will shift the average flower color
towards the darker end of the spectrum, an
example of directional selection. - B—By successfully transforming your E. coli,
you are giving it the gene that enables it to sur-
vive in the presence of ampicillin (something the
bacteria are unable to do otherwise). Therefore,
you have successfully transformed your culture if
it grows on ampicillin-containing agar, but the
control culture without the plasmid dies. - Which of the following would indicate you suc-
cessfully transformed your E. coliculture with
the plasmid containing the gene for ampicillin
resistance?
A. The ampicillin-containing agar plates would
show growth from your control culture
(E. coli without the plasmid), but not your
transformed culture.
B. The ampicillin-containing agar plates would
show growth from your transformed cul-
ture, but not the control.
C. The transformed culture would not grow on
the agar-only plates.
D. Both the transformed E. coli and the
untransformedE. coliwould grow on the
plain agar plates.