We publish practice problems on our social media pages. Here's where you can find the correct answers—and explanations.

*n*, 2*x*); this is not the same as being diploid (2n, 1*x*) (choice D is false and therefore the correct answer). Replication occurs before both mitosis and meiosis (choice A is true and can be eliminated), and the nuclear membrane is taken apart to allow for proper division of genetic material in both (choice B is true and can be eliminated). Once the nuclear membrane is gone, microtubules are instrumental in the physical movement to achieve proper genetic division for both (choice C is true and can be eliminated).

*q* = 0.2 and thus 1 – 0.2 = 0.8 = *p*. The question is looking for carriers, which would mean heterozygous individuals. This is represented by 2*pq* = 2(0.8)(0.2) = 0.32 (choice B is correct). Choice A represents the frequency of homozygous recessives (0.22 = 0.04) and not the frequency of carriers. Choice C represents the frequency of homozygous dominants (0.82 = 0.64), and choice D represents the frequency of the dominant allele.

*y*-displacement traveled during each half of the flight), it is useful to remember the fact that, in the absence of air resistance, time up equals time down. This allows you to focus on either the first half of the trip (the way up) or the second half (the way down). Since you are not given the initial launch velocity, it is easier to look at the second half of the journey, where the initial vertical velocity is zero. Calling the positive *y*-direction downward, you have *ay* = *g* and *t* = 4 s. You want *y* and you’re missing *vy*, so use Big 5 #3: *y* = *v*0*y**t* + (1/2)*ayt*2; you have *y* = 0 + (1/2)(10 m/s2)(4 s)2 = 80 m, or choice B. Alternatively, you would get the same answer by focusing on the way up and using *y* = *vyt* – (1/2)*ayt*2. Note that the angle does not factor into the answer.

*K*d for receptors and their ligands is analogous to *K*m in enzyme-substrate interactions. It is the concentration of ligand at which half the receptors are occupied, and it will increase in the presence of a competitive antagonist (higher concentrations of ligand are required to reach the same saturation point (choice D is wrong).

*S*, choice A is wrong), and transcript folding (as with protein folding), results in a decrease in degree of rotational freedom as the macromolecule forms new interactions (choice C is wrong).

*ΔG *is not affected by the addition of a catalyst; catalysts only affect the kinetics of a reaction, not the thermodynamics. Catalysts are not always specific. Heat and sparks are good general catalysts, but are not specific for particular reactions (choice B is wrong, and choice D is correct).