true

SERIOUSLY 😂

hahaha

Same are you also taking genetics?

Very kind to take the time to write - thanks!

Hahaha

I agree.

Thanks for commenting. Yes, you're absolutely right (please confirm your suspicion with the written description of the video).

Glad it was, at least, entertaining!

No - the video is flipped horizontally after recording, so the writing appears normally

Joseph Ross I was freaked out at first but then I was like: ahhhh... So cheeky!

after this video this was the only question i had

I'm conflicted on how to respond. On one hand, I think it is a complement. On the other, I'm not sure that "soothing" is what I should be aiming for in a video lecture! As long as viewers are staying engaged and not falling asleep, then I'll own it! Thanks for taking the time to comment.

@@JosephRoss Well I mean, I saw this video while freaking out thinking I wasn't going to be able to teach it the next day, so I needed some soothing!

Krista Fincke Ah, I understand. Right! You definitely don't want instruction to be stressful!

My apologies: I don't have time to provide individual responses to particular cases. Briefly, though, I'll note that genetic mapping makes many assumptions, and whether those assumptions apply to any particular case can make calculations behave unexpectedly. For example, my video assumes complete crossover interference, which isn't always the case. If you have to account for the possibility of multiple crossovers, that can change the estimated genetic distance. That's just one example of a caveat; there are others.

@@JosephRoss Thank you, I just realized an error in the problem, I appreciate that you spent the time to answer my question!

No, I have not yet - thanks for the suggestion

@@JosephRoss You're welcome sir. I want to say that your teaching is very good. And your videos are really helpful to me. So do make videos on different models of crossing over .🙏🙂

Thanks for the kind comment. I did catch that issue and noted it in the video description, but very few people probably look there! I wish that KZfaq had an easy way of making these sorts of notes in the context of the video itself, so I could point this out at that specific point in the video

I am filmed as it appears (through the glass board) and then the video is flipped across the vertical axis, so the writing looks forward to you but I am reversed (e.g. I'm not left-handed)

@@JosephRoss oh.. that's a neat trick

A-C is the largest genetic distance. Thus, gene B must be in between those two (see also the comments in the video's description)

@@JosephRoss it's written that you have, between B-C 40.16 CM, and between A-C 21.75 CM I don't see that it is the largest genetic distance but more between B-C (40.16 CM)

@@Odin_valkiri I don't understand your question, but this might help: take a look at the text description underneath the video - I note there that I made a mistake in the video, and so that text description might address your concern.

Yes, I should reiterate that an assumption I made in this video is that there are no multiple crossover events (double, quadruple, etc.). In some circumstances, this is a reasonable assumption, and in other circumstances not.

Hi Erik - what do you have in mind, as far as a collaboration?

Unfortunately, that's just a videography trick (I write normally and after recording the video is flipped so that the writing appears normal to the viewer)

Absolutely right. In a sense, yes, I've forgotten about double (and triple, and quadruple…) crossovers. In actuality, I ignored them on purpose. But, I should have explicitly said that I was making such an assumption. So, I'm revising the video description to make this point. It so happens that my research organism exhibits complete crossover interference, so I'm in the habit of assuming that there are no multiple-crossovers, but that is not the case for every organism. Thanks for pointing this out!

Hello - you're absolutely right. I had already noted this in the written video description under the video (which you have to expand to read). I wish that KZfaq had an easy way for me to edit the video or another way for me to more obviously point out this error. Thanks for writing.

Crossing over does occur in every individual in every generation (P0, F1, F2…). However, in an individual that has a completely homozygous genotype (here: both of the P0s and also the F1 tester), I don't show crossing over, because any crossing over has no effect on their gamete haplotypes: a completely homozygous chromosome always produces the same gamete haplotype regardless of crossing over. For example, crossing over certainly occurs in the P0 with genotype A1B1C1/A1B1C1, but no matter where the recombination breakpoint occurs, that individual still only produces A1B1C1 gametes. So, I ignore it for simplicity. It is recombination during F1 meiosis in the trihybrid that causes the recombinant haplotypes in the F2 offspring. So, the only recombination that I'm explicitly describing in this video is indeed F1 generation crossing over.

@@JosephRoss thank you so much! that makes sense.

Thanks - I did already note in the video description that I made an error in the video; that error, I think, also explains your concern. I appreciate your comment, and I wish that KZfaq had a better tool for me to point this out in the video itself!

My apologies for the confusion: it is probably because I made a mistake in the video, which I explain in the comments immediately underneath the video. I'm working to re-record the video without the mistake. If you inadvertently caught my mistake, then it sounds like you know how mapping works!

Joseph Ross Thanks for clearing that up! I don’t really read the description so I missed it. Anyway, your video helped in my genetics exam so thanks and keep doing what you’re doing! 😊

Correct. I should go back and re-do the video, but in the text notes, I did point out this mistake: B-C is calculated as 21.75 cM. The reason that the A-C genetic distance calculated from the recombination data (40.16 cM) is less than the sum of the A-B and B-C distances (41.67) is because of double-recombinants (the two haplotypes with total observations of only 4 and 5). Because we don't initially know which classes of haplotypes are the double-recombinants, we will always under-estimate the actual genetic distance. Once the order of loci is determined, then yes, one can go back and correct (but that isn't necessary: the sum of smaller intervals, like A-B and B-C) will always result in a more accurate estimation of genetic distance.

YES techHeaven you are right

@@JosephRoss ohhhhhhhhhhhh

I hate to break the spell, but…I write normally. After taping, the entire video is flipped so that writing appears properly to the viewer. In other words: I'm not left-handed, but it looks like I'm writing with my left hand in the video. If I had writing on my shirt (for example), then it would look reversed to you.

Joseph Ross You, sir, are a genius.

You are absolutely right - good catch! (but, please note that I do point out this error in the text description just under the video). Hopefully someday I'll have a chance to re-record the video.