I had the absolute displeasure of listening to this so-called "Dr. Heather Tienson-Tseng" for the past 10 weeks. Let me start by sharing with you an excerpt from the final email to the class as she posts final grades:
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" I know some of you may be disappointed with your grade, and I am sorry about that. However, they are final. Grades cannot be changed; no matter how much you whine or beg. "
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Whine or beg. These are the words she uses to address her class. I have never met such an arrogant, rude, and downright unpleasant person in my life. Let me put the personality complaints aside and tell you about the exams. The first exam was incredibly easy with a median score of 84%. Being so high, she sends us an email about how she is surprised and essentially wants/expects a lower average. We all get very nervous for the second exam, so we study very hard to prepare. Boom, second exam results come in and the average is a 50% with a HIGHEST SCORE of a 72%. The exam was IMPOSSIBLE to do well on, and was obviously designed for students to fail (hence the average). She comes into the class smiling the next day, without any sort of apology for such a terrible exam. I knew it was completely on purpose to lower the overall average grades of the class. Final exam was not so bad with an average of a 73%. A 90% overall grade was the A cutoff.
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The course was rather boring and uninteresting. The material was super easy until the end of the second midterm material where it suddenly picked up and was way too fast. She decided to lecture a massive amount of material in week 10 when our final was on Sunday (so Friday lecture was tested on in depth less than 2 days later). She never told us anything about what we were expected to know for exams except "look at the learning outcomes." This was hugely misleading since none of the learning outcomes for a particular section said we would be required to draw the mechanism of RNA splicing, but there it is on the 50 minute midterm. She was so unclear on what we had to know that we would spend hours memorizing meaningless details that were never tested on.
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The curve in this class is extremely weak. You barely get 3-4% grade boost at the B+/A levels. With a midterm of 50% average. Tell me how this is fair to the students. Clearly, she does not care about her students and is teaching purely for a paycheck and to banter to her top 2 favorite students about how women scientists don't get recognized for Nobel prizes.
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If you can avoid her, then BY ALL MEANS steer clear. Her course is boring, unforgiving in terms of grades at the B+/A levels, and she doesn't show any care for her students' success. She wrote a midterm to be impossible on purpose to bring her class average down because she simply doesn't want to give out more than 20% A's. What kind of professor does this?
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A bad one.

Ok.. let me start by saying that it doesn’t matter how much you study or how well you understand the material, you constantly feel inadequate because of the style and grading keys of the exams. You will have to fill 10 empty pages with correct answers within 50 minutes which makes it very hard to complete. Do not overestimate yourself just because you only have to get 75 points out of 100 points to get full credit on midterms( maximum points are cutoff at 75). Because you would have to write down the grading key, not similar plausible answers. If its possible, please skip this instructor for this course. After having midterms that are averaged almost 50%(37.75 out of 75), it is unreasonable to have a cutoff of 90% for an A.
I have never worked so hard for a class in my life!
Its safe to assume that she somewhat enjoyed our struggle!
Please do something more useful instead with your time
The courses must not be designed based on what exact words to use when answering questions. Thats why synonyms exist! Good luck getting points if you don’t read her mind and extract her choice of words. This is just one of many different issues. Feel free to read all other comments to aknowledge yourself of other issues. :)
I do not intent to be disrespectful. This is the nicest possible way I can express my opinion about this instructor and this course.
I wish very best of luck to people who take her due to unavoidable reasons. Trust me, you need it..

To be honest, Professor Tienson was a caring professor. She was understanding due to the circumstances that arose because of COVID-19- she made our tests open note, open book, and open friend. Although she usually lectures at a fast pace, she is usually willing to answer any questions. Her lectures are not always the most engaging, but she does cover a lot of material. Her clicker questions are also hard asf and borderline unfair sometimes, but her lectures and discussions did prepare us sufficiently for exams.

Most of these reviews criticizing Heather are based on pre-covid classes - but a lot of their points are still valid. Online, however, it's become a LOT easier to get an A. The grading scheme consisted of 15% pre-class assignments, 25% post-class assignments, 30% exams, and 30% group project. The project is your best bet to boost your grade - the exams are abhorrently written/graded and in my opinion were worse than 153C. The questions aren't too bad but the rubric is so specific and picky that exams seem more like she's testing how well we can read her mind instead of actually understanding the material. I had about a 50 something % exam average throughout the quarter but ended up scraping an A- out of the class.
Anyways basically it's just one of those classes where you feel like you're failing all quarter but it ends up boosting your GPA (hopefully).

I feel like these reviews do not do professor Teinson justice. Maybe it was because of the circumstances of the quarter, but she was by far one of the most understanding professors I’ve ever had in college. She made sure we all understood the material, answered every question one had and was very nice throughout the whole quarter. Despite her last review I applaud her for going above and beyond for this quarter. She relieved much of the stress from a difficult class during a difficult circumstance and I would take her again for a different class if given the opportunity. The exams are difficult and clicker points are based on correct answers, but I feel lucky to have had professor teinson this quarter!

I think I'm about to be the first positive review of Dr. Tienson for 153B. Bear in mind that I did get an A in this class so that probably makes me biased.
This class is by no means easy. I would still argue that 153C is harder than 153B, but 153B is still no joke. There's not as much material in 153B but Tienson structures the class in a way that still makes it hard lol. However, I still think Dr. Tienson is one of the better choices for 153B. I studied so much for the midterm exams and it was reflected in my scores. The class did really well on the first midterm and then it plummeted to a 50% average on the second one (I got a 96% on the first midterm and 72% on the second midterm). I thought the final exam was really hard like the average was 110/200 and I only got 120/200. I left a lot of part B questions blank but still managed to do alright. I was told by so many people that Dr. Tienson isn't as knowledgeable about 153B as much as 153A, which I think is true (she takes all her slides/some exam material from Albert Courey, aka the really good professor of 153B before the department stupidly confined him to teaching the 14 series), but I still think she knew what she was talking about. I feel that I have learned a lot and that this class prepared me for understanding biochem in grad school/my future career. Of course I can understand why she has negative reviews, I also had days where I came into class just thinking that I hated this class. But actually Tienson is really nice, I think she is misunderstood by a lot of people. Again, I don't blame them, as the class structure is kind of annoying and the exams are hard. I just don't want everyone going into this class hating her you know? Give her a break, she just gave birth to a baby!
My tips for doing well in this class:
-The TAs sometimes don't give you points when you deserve it! One time I submitted a regrade request for a point and the TA still rejected it, even though I knew I was right. That's when you take your case to Dr. Tienson; she gave me the point and said the TA was wrong. So speak up for yourself and really check how your exam was graded on gradescope! You may be able to get some points back.
-Go to the discussion of a TA who will just give you the answers to the discussion worksheet. Don't waste your time going to the TA that draws out the entire discussion by having you work on them during section.
-Take the group exams and actually try on them because you have access to internet/your classmates. She says on the syllabus that you only get points back if you get a higher percentage on the group exam than on your midterm. I got a 9/10 on the first group exam so I thought it was a waste of time to take it at first, but at the end of the quarter I saw that she still added a few points to my midterm score!
-Read the textbook. I couldn't get my hands on the Voet one but Lehninger was good enough. The textbook can be too complicated/too much information sometimes so try to take notes while having the lecture slides out so you know what's worth reading from the textbook.
-Don't waste your time going to tutorial on Tuesdays unless you're genuinely interested. Also same goes for the LA workshops. I found it more helpful to just watch the bruincasts of the LA workshops because you can watch it at 2x speed and skip towards the end of the class where the LAs give you the answers to the worksheet. Make sure you do the LA worksheet every week, one of the problems on there might appear on your midterm. It happened to us. There was a problem on an LA worksheet to draw out the mechanism of intron lariat formation, and the next day it appeared on the second midterm exam. This question screwed a lot of people over on the exam, but not those who knew it already from the LA workshop!
-On the exams, do all the part A questions first, then go back to part B. For questions you aren't sure how to answer, leave them for last. It is more important for you to be thorough about questions where you feel totally confident that you know how to explain it rather than wasting time guessing how to answer a question you're unsure about. You won't get any points for just writing something down, you will get points for covering all your bases when expounding upon your correct answers. I know some of us may have the whole "don't leave anything blank" mentality (I had that too) but I learned that in this class, you get more points by perfecting a few of your answers rather than half-assing a lot of them.

Honestly, these reviews are not fair at all. Idk if circumstances have changed or what the issue is but, to me, Dr. Tseng is by far one of the best teachers I’ve ever had. You can tell that she puts in soooo much time structuring the class and making the lectures fun and interesting. She does such a good job presenting the information that learning Biochem really doesn’t feel all that tedious. She was so patient and was always willing to answer any questions if people were confused about something during lecture. She provides plenty of extra credit, as well as additional resources to help you be successful in her class. If you take good notes during lectures, do the discussion and tutorial worksheets and maybe just a few study questions, there’s no reason why you shouldn’t be able to get an A in her class. I went into this class really hating biochemistry after taking 153A and 153C with a different professor; but I left this class really loving it. Overall, would strongly recommend! Thank you, Dr. Tseng!

Professor Tienson was great during the quarter that I studied 153B. The material in itself is fairly difficult but it IS an upper div so it's basically expected. Her lectures were recorded and if you actually rewatch the lectures and attend office hours, it will help a lot. The only thing that erked me in the wrong way was the peer review assignments because they can be really subjective when it comes to the grading by your peers. Aside from that, we had a group project for our final instead of a huge cumulative final. We had 3 mini midterms that we had to do ourselves (no help from others) which were fairly long but do-able. My group was amazing, and if you take her class, the key is COMMUNICATION and weekly group meetings. She also has something called "tutor" that's done twice a week. One of these "tutor" sessions were about actually research articles that she will have on the exam. The second "tutorial" is an LA led workshop which was SUPER DUPER helpful. Never really read or opened the book. Extra credit up to 21 points.

She is a very very bad professor. This is all I have to say after taking her class.

When you are in the classroom and hear the lecturer talks like "ah...today...ah...we gonna talk about ah...ah...DNA...ah..."; guess what? You are in the class of Dr. Tienson!
She uses the iclicker to take attendance, but the only purpose of her lecture is to torture her students' ears. She doesn't know much biochemistry, not even good at reading from the slides.
She can't even produce a complete sentence without saying "ah..ah..ah..", but she is truly a master in annoying people.

The exams were graded using gradescope, and please be informed that you almost can never get a score that you expect because the answer key really contains everything one can think of, and it is impossible to write them all down within a such short time.
Her class has made me to doubt myself...Indeed, I thought that I was crazy, so I went to see a shrink. Fortunately, after a few sessions, the shrink told me that the problem wasn't on me, but there are some serious mental issues with Dr. Tienson. It is extremely disappointing that such a pathetic "lecturer" teaches at UCLA.