Gas chromatography and thin layer chromatography differ by the phases of both the mobile and stationary phases. In gas chromatography, the mobile phase is a gas and the stationary phase is a liquid. In thin layer chromatography, the mobile phase is a liquid and the stationary phase is a solid.

In the normal phase chromatography system described, the most nonpolar compound would elute first and the most polar compound would elute last. The silica stationary phase will interact with more polar molecules, while the hexane mobile phase will carry nonpolar molecules. This would slow the progress of polar molecules as they bond to the silica, and enhance the progress of nonpolar molecules as they interact with the mobile phase.

Compound C is the most nonpolar compound because it contains only hydrogen and carbon. Compounds A and B are more polar because of the presence of oxygen, and hence the presence of polarized carbon-oxygen bonds. The alcohol group of compound B makes this compound the most polar of the three molecules by virtue of hydrogen bonding capabilities as well as the carbon-oxygen dipole. Compound B would thus elute last.

The R_f factor is a ratio of the compound's travel distance compared to the solvent's travel distance; this value will always be between 0 and 1. As a result, a nonpolar compound would not be able to travel twice the distance or have twice the R_f factor as the mystery compound. This would result in a value of 1.2.

The only thing we can predict confidently is that a more polar compound would travel a shorter distance than the mystery compound, which result in a lower R_f factor. 

The necessary genotype for a female zygote is XX.

The mother will share this XX genotype (since she is also female) and will contribute one X-chromosome. The father, however, will be male and have the genotype XY. This means he has a 50% chance of passing on an X-chromosome and a 50% chance of passing on a Y-chromosome. If the zygote inherits a Y-chromosome from the father's sperm, then the offspring will be male. If the zygote inherits an X-chromosome from the father's sperm, then the resulting genotype will be XX and the offspring will be female.

Totipotent cells have the ability to propogate and differentiate into any cell types, including the trophoblast. They are different from stem cells, which could be considered multipotent (able to differentiate into multiple tissue types) or pleuripotent (able to differentiate into any major tissue type, but cannot create trophoblast). The only truly totipotent cells are the first two blastomeres.

Most cells contain a complete genome, but not all genes are activated in each cell. Activation of particular genes produces appropriate protein function.

The endoderm develops into a number of internal organs, including the lung, which are vital for breathing.

The kidneys (urine production), muscles (movement), and blood vessels (blood circulation) develop from the mesoderm. The brain (thought) develops from the ectoderm.

This question is targeting your knowledge of the circulatory system. Since the medication has a short half-life, it is necessary that it be carried by the patient's blood stream to the tumor as quickly as possible. Blood travels through the right side of the heart, to the lungs, through the left side of the heart, then to the body. Therefore, inhalation of a chemical would require the least amount of traveling (Lungs, Left Atrium, Left Ventricle, Body). Each other method of administration, including IV, would require more time to travel to the brain. For example, for the IV answer choice, the pathway would be Vein, Right Atrium, Right Ventricle, Lungs, Left Atrium, Left Ventricle, Body.

Like many biological functions, thermoregulation is controlled by a negative feedback system. This is because the response is the opposite of the input: a hot environment triggers cooling, while a cool environment triggers heating. A positive feedback system would intensify a response in the same direction as the input. If a positive feedback mechanisms were true of regulating body temperature, cold weather would trigger sweating and dilation of blood vessels. The result would be that you would get even more cold, which would not be good for maintaining homeostasis. Hormones do help regulate many body functions, but they are not the best description of how body temperature is controlled.

In its home environment, the fresh water fish will be in equilibrium with its surroundings. As such, it will essentially be isotonic with a fresh water solution. This represents a relatively low solute concentration in the fish's body.

When we transfer this fish to a medium that is more densely concentrated with solute molecules, the fresh-water fish will be hypotonic in relation to the external medium. The salt in the surrounding water will cause the external environment to be more concentrated than the body of the fish. As a result, the fish will quickly become dehydrated as water exits its body.

Hypertonic and hyperosmotic are synonyms, which both refer to greater concentrations than the surroundings (opposite the scenario described).