258 ❯ STEP 4. Review the Knowledge You Need to Score High
nongerminating peas that will have a lower baseline respiration rate, (2) a control group
that measures the change in oxygen due to pressure and temperature changes, and (3) an
experimental group that contains the group whose respiration rate you want to measure.
Investigation 7: Cell Division: Mitosis and Meiosis- To determine experimentally the percentage of cells in a particular stage of the cell cycle,
examine an onion root slide and count the number of cells per stage. Divide the number
in each stage by the total number of cells to determine the relative percentages. - To determine how far a gene for an ascomycete fungus is from its centromere, cross a
wild-type strain with a mutant and examine the patterns among the ascospores. A ratio
of 4:4 means no crossover occurred, whereas ratios of 2:2:2:2 or 2:4:2 indicate crossing
over did occur. Total number of crossover divided by total number of offspring equals
the percent crossover. Divide this by 2 to get distance from the centromere.
Investigation 8: Biotechnology: Bacterial Transformation - To run a transformation, add ampicillin-sensitive bacteria to two tubes, and to only
one of the two, add a plasmid containing both the gene you would like to transform
and the gene for ampicillin resistance. The other tube is the control. Ice the two tubes
for 15 minutes, then quickly heat-shock the cells into picking up foreign DNA. Ice the
tubes again, spread the bacteria out on ampicillin-coated plates, and incubate overnight.
If transformation occurs, your bacteria will grow on the ampicillin plate.
Investigation 9: Biotechnology: Restriction Enzyme Analysis of DNA - Gel electrophoresis can be used in court to determine if an individual committed a crime
or if an individual is the parent of a particular child. Each person has a particular DNA
fingerprint. When that individual’s DNA is cut with restriction enzymes and run on an
electrophoresis gel, it will show a unique pattern that only that person has. By matching
a person’s DNA fingerprint with that of the child of interest or the evidence from the
crime scene, proper identifications can be made.
Investigation 10: Energy Dynamics - A simple model system can be used to track how much energy is transferred from a single
producer (plant) to a single consumer (caterpillars). - By weighing the amount of plant eaten by the caterpillars (and the amount of the plant
excreted), it is possible to calculate the percent of the plant’s energy that was either incor-
porated into the caterpillar’s body or used in cellular respiration. - These are methods for estimating the efficiency of transfer of energy from producer to
consumer.
Investigation 11: Transpiration - To design an experiment to test the effects of various environmental factors on the rate of
transpiration, measure the amount of water that evaporates from the surface of plants over
a certain amount of time under normal conditions. You can do this using the whole-plant
method or by using a piece of equipment known as a potometer, a device that measures
water loss by plants. Compare the normal rate with the rates obtained when the temper-
ature, humidity, airflow, or light intensity is altered. If you run an experiment of this
nature, it is important to measure the surface area of the leaves involved because larger
surface areas can transpire more water more quickly.