Red blood cells are responsible for transporting oxygen in the blood. People with sickle cell anemia were born with a defective gene that results in sickle-shaped red blood cells. Individuals with the disease often suffer pain in their extremities due to the build-up of these cells causing blockages in the blood vessels. The shape of the blood cells also reduces the amount of oxygen transported in the blood.

The image below shows a side-by-side comparison of normal and sickle-shaped red blood cells.

Image courtesy of NIH.

Which of the following medical treatments would cause changes to the genetic material of the patient?
A.
replacing the blood in the body via transfusions
B.
replacing the malfunctioning gene with a healthy copy
C.
providing drugs to increase oxygen levels in the blood
D.
targeting and killing sickle cell

Which are forms of nitrogen that are usable by humans

If the birth rate of a population of dolphins is 2.0, the death rate is 0.5, and the population size is 100, what is this dolphin's population growth?

Experiments in environmental toxicology can sometimes be manipulative experiments in which the researcher actively chooses and manipulates the independent variable. in hunt's study, for example, dosages of bpa were manipulated and the effects were measured. in manipulative studies, the researcher controls all the other variables in the experiment, so any health effects observed in the test subjects can be attributed to differences in the independent variable. in other cases, researchers use natural experiments in which the dependent variable (typically a measure of organism health) is measured under differing contexts that are not manipulated. say, for example, that an accidental chemical spill contaminates five ponds. to determine the possible effects of the toxic chemical on frogs, a researcher could compare the hatching rate of frog eggs laid in those five ponds to the hatching rate of eggs laid in five uncontaminated ponds nearby. this would be an example of a natural experiment because concentrations of the toxic chemical in the ponds were not controlled by the experimenter, but rather resulted from the chemical spill. drag type of experiment on the left to the example of experiment on the right. blood concentrations of bpa in college students are compared to their recent manipulative consumption of canned food items 2. the feeding behavior of fish in streams that receive acidic runoff from strip mines is compared to the feeding behavior of fish in unaffected streams. the deformity rate in baby birds from nests in pesticide-sprayed fields is compared to the deformity rate in birds from nests in unsprayed fields 4 tumor development is compared in mice exposed to five dosages of a known carcinogen in the laboratory foraging activity levels are compared in tadpoles exposed to four concentrations of toxic metals in the laboratory. growth of corn plants is compared in field plots sprayed with three different dosage: s of weed killer 7 bpa concentrations in the urine of people with diabetes are compared to bpa concentrations in the urine of people without diabetes - natural; manipulative