Hey everyone! We're excited to be launching our Frameshift MCAT Lessons of the Week, an email we send out every Sunday night that's packed with MCAT tips and lessons. This email includes some of our very best advice on content topics, strategy, test-taking tactics, and more, all absolutely free! All takeaways are written by our MCAT experts (myself and @FrameshiftAndrew) and relate to our livestreams held during the prior week.
Just a reminder that if you sign up by this Sunday at 8pm, you'll receive our next Lessons of the Week email! You can sign up or learn more here: frameshiftmcat.com/lessons
For anyone who's curious, here are some of the lessons from last week's email! Note that we organize these lessons according to the corresponding recent livestream (which we hold at least once per day).
Hardy-Weinberg Calculations
The vast majority of H-W calculation mistakes stem from confusion about which equation to use: p + q = 1 or p2 + 2pq + q2 = 1.
p + q = 1 should be used for allele frequencies. Don’t plug anything in to this equation unless it’s the frequency of either the dominant or the recessive allele!
p2 + 2pq + q2 = 1 should be used for genotype frequencies.
p2 + 2pq + q2 = 1 can also be used for phenotypes, but keep in mind that the dominant phenotype includes both p2and 2pq.
Experimental Flaws and Limitations on the MCAT
Experimental flaws tend to be tested in hypothetical questions, while experimental limitations are most relevant for passages.
Be very careful before pointing to sample size or ethical issues as experimental flaws; these can be legitimate in some cases, but are often trap answer choices because they’re superficially appealing.
Studies must be interpreted within their limitations; for example, a cross-sectional design cannot support causal inferences.
CARS Passage Review
Pay close attention to relative timing words, such as “before,” “after,” “later than,” etc.! Answers to questions about the author’s stance (or views on some information) should always match the author’s tone throughout the passage.
Passage descriptions of two things as similar or equal (“the same as,” “equally influential,” etc.) can be just as important as contrasts (“superior to,” etc.), but they tend to be easier to overlook.
Science Diagram Review: The lac Operon
Operons are an elegant way for bacteria to respond efficiently to environmental conditions.
There are two functional components of the lac operon: (1) whether or not the repressor is bound to allolactose determines whether these genes can be expressed at all; (2) whether the CAP-cAMP complex is present at the CPA binding site indicates whether it is urgent.
The lac operon is a negative inducible operon (default = off); the trp operon is negative repressible (default = on). Positive operons involve an activator protein, but the lac and trp operons are most frequently tested.
Here are a few of the lessons from our most recent email! To receive all of our weekly lessons starting this Sunday, sign up anytime at frameshiftmcat.com/lessons.
Torque
Equilibrium in physics can be translational or rotational.
Translational: no acceleration and no net force, although the object could still be traveling at a constant velocity (or, alternatively, standing still)
Rotational: no angular acceleration and no net torque, although the object could still be rotating at a constant velocity (or, alternatively, not rotating at all)
Torque is governed by the equation 𝜏 = r F sin(θ). An angle (θ) of 90° maximizes torque, while an angle of 0° yields a torque of zero.
Most torque questions involve relatively simple applications of this equation. However, watch out for rare cases in which the lever arm has mass and the fulcrum is off-center; in these situations, the torque from the lever arm’s weight must be accounted for.
The eternal dilemma: going back to the passage or using content knowledge
Few passage-associated questions (≤1 per passage) are purely content-driven.
Most questions require a combination of passage and content knowledge; even relatively “pure” passage-based questions draw upon your understanding of the passage based on science knowledge.
When reviewing, compare and contrast “low-knowledge” vs. “high-knowledge” approaches to questions—it can be possible to get a question right, or at least to eliminate some options, based on careful application of passage information even when you lack relevant science knowledge.
MCAT math often allows (and rewards) rounding and estimation, so answer choices are often relatively far apart. In the rare cases when they aren’t, the question is likely solvable with passage information or with a math shortcut/tactic.
Scientific notation can be manipulated to yield the same math expression, but in terms that are easier to deal with. This can be used to approach situations in which a smaller numerator is divided by a larger denominator, or when the numbers involved are originally ugly decimals.
To estimate the negative logarithm of a number in scientific notation, swap the sign of the exponent and subtract zero point the coefficientfrom that value.
...and some more examples from our most recent email! Note that each week's email contains eleven of these sets of lessons, one for each of the prior week's livestreams and passage review sessions. Check out frameshiftmcat.com/lessons anytime for more info!
Strategies for effectively flagging questions
Question flagging serves two key purposes:
It can keep you from lingering excessively on individual questions, which is surprisingly important.
It’s extremely helpful with managing any extra time you have left at the end of a section.
If you’re using flagging for a goal other than the above two purposes, it’s very possible that you’re using this tool ineffectively.
Some mistakes to avoid with question flagging:
Over-flagging (keep it to 10 or [ideally] fewer questions per section)
Flagging every question that you’re unsure about
Flagging every question where you’re stuck between two answers; this can actually lose you points, for multiple reasons
MCAT students tend to understand DNA and RNA pretty well, but it can feel like that knowledge goes out the window when you’re presented with an actual diagram. Practice examining the structures of nucleotides and nucleic acids (from the bonds involved to the charges on phosphate groups) to avoid this issue.
You really do need to know the structures of the nitrogenous bases!
Understanding the carbon numberingon ribose and deoxyribose is incredibly helpful. Remember, carbon 1 is the carbon directly attached to the nitrogenous base (and the oxygen of the monosaccharide ring).
The “deoxy” in “deoxyribose” refers to the lack of a 2′ -OH, not a 3′ -OH.
CARS passage review: science and religion in Byzantium
For a passage like this one that deals with a lot of obscure historical information, focus on keeping track of (a) names, (b) dates, and (c) how names and dates relate to different perspectives that are presented.
Incorrect answer choices for “main idea”-style questions may restate passage information, while being incorrect because they fail to address the whole picture.
Fairly frequently, two answer choices can be eliminated fairly easily, while the distinction between the remaining two might not be obvious. In such cases, eliminating two incorrect answers and guessing may be an acceptable strategy to preserve your own mental well-being and energy to engage with the other questions in the passage (and the other passages in the section!).
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