Three-point mapping and gene order

[@nicktokar2459]

Even when you make an error, it makes more sense than when my professor explains it correctly.

[@abbiravindhran8424]

true

[@TheCocoKayyy]

SERIOUSLY 😂

[@ARTDEVGRU247]

hahaha

[@tomlangford1999]

been trying to understand this for the last 5 hours, and this guy explains it in 15 minutes and I understand it

[@forparasocialpurposesonly]

Same are you also taking genetics?

[@zenzi2244]

Even 3 years later this video is helping confused students like me. This method of mapping everything out individually made it completely clear how to work it out. FANTASTIC work, you are an excellent teacher and should take pride in that fact!

[@JosephRoss]

Very kind to take the time to write - thanks!

[@ngohuynhlillian]

A blessed man, you are a blessed man and I wish you bliss with everything that is good in life

[@raquelpurpleboxes]

Hahaha

[@aadhavyasivakumaran5281]

I agree.

[@alimo2823]

been stuck on this since the midterm and it took 15 minutes to understand it for the final. truly remarkable and i appreciate you for this!!

[@matthewlee4834]

I cannot stress enough how important this video is to me. You really truly saved my grade and sanity. Neither the textbook nor professor was helping, and all it took was one video for me to finally understand. Thank you so much

[@cryptidcorvid]

this is *by far* the best way i've ever seen this explained, thank you

[@sarahholland5980]

I was so ridiculously confused by this concept, I've rewatched the lecture multiple times and still didn't understand. This made so much sense. Thank you!!!!!

[@sirevgiio5896]

My friend, you are amazing and this was incredibly helpful, thank you so much. I've been trying to understand this for days, and now I finally feel like I understand all of it.

[@kelliesutfin6670]

I know this was posted 4 years ago but thank you! I've spent two weeks not understanding this and you just helped me learn it!

[@lauraschulz7335]

Thank you!! This was so helpful, definitely the best video I found on this topic

[@courtneyfairchild7884]

THANK YOU SO MUCH!!! I've been trying to figure this out for HOURS and you help me crack the code in like 20 minutes!!!!!

[@sameerdaya2620]

u made my life easier im tryin understand this the past 24 hours and you explained it in minutes

[@thuyxuan2209]

Thank you so so so much! This saved me. This is much easier and less confusing than the method I learned in class! Gotta share it with all my friends!

[@jojonyquist6953]

Amazingly helpful video! So diligent at explaining things.

[@yuzhongzhang4002]

holy crap thanks for making my life so much easier!

[@cnsmit]

The best way I've ever seen this explained. Thank you.

[@tylerlowe1484]

This is the greatest three-point mapping tutorial ever to exist upon the face of the earth.

[@ikhares]

you're a king and you deserve the world thank you for saving my gpa

[@Phyto.]

This is hands down the most efficient way to do 3 point crosses. Thank you SOOO much!!

[@letzxplor7835]

12:50 it is 261, not 482😊. He accidentally put it for B to C recombinants, as he was referring it from his notes. And thus obey the additive rule🎉. Thank you so much❤for this crystal clear explanation and i want to become someone like you when it comes about explaining science things. Keep going🎉 You earned a subscriber..

[@JosephRoss]

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 KZbin 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

[@raquelpurpleboxes]

Thank you for explaining with such patience 🙏

[@matthewhynes3959]

Great video! You really helped me to understand this tricky subject!

[@mithradat1283]

That was nice, clean and complete. Thanks a lot.

[@Joobeanie]

i thought that he was writing backwards and was like damn dude this guy is cold asf...he can write everything backwards perfectly???!!!! then I realized they probably just flipped the video so we see it how he sees it...im dumb halp haha

[@JosephRoss]

Glad it was, at least, entertaining!

[@pratadhikari5377]

For the A-C recombinant addition, how do you get 261 when you add all the Rs: 128+114+116+124. I am getting 482 for A-C not distance for B-C. I think you flipped the numbers of Rs for B-C and A-C. B-C should be 261 R A-C should be 482 R

[@JosephRoss]

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

[@lucascusanelli4013]

Your explanation was so helpful thankyou so much

[@kristafincke61]

You have the most soothing voice!

[@JosephRoss]

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.

[@kristafincke61]

@@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!

[@JosephRoss]

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

[@sweetalana6900]

This was really helpful .One of the best ways to solve these problems.

[@sciences9645]

Interesting, But always don't forget that the two least frequent haplotypes are where DCO (double cross over) existed and always you have to count them as recombinants and the distance from A -C should be like (128+114+116+124+5+4 = 491/1200 = 0.409), i.e. 40.92cM apart.

[@JosephRoss]

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.

[@irwinleventer2851]

Thank you so much you're so helpful!

[@fredd298]

Impressive that you can write backwards so fast with your right hand.

[@JosephRoss]

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)

[@anisheshdas362]

Thank you so much.This helped me a lot.

[@arjetaallamani5930]

This was

[@ciaramurphy3117]

very helpful and clear video

[@ikz8439]

i actually understood this. thank you man!

[@Ponce904]

Thanks for the excellent explanation!

[@rmn147]

Does he have to write backwards

[@JosephRoss]

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

[@johnthebossbudileanu4530]

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

[@jacobmcclellan4740]

after this video this was the only question i had

[@annavitenkova8936]

Thank you very much for a great explanation!

[@LiamDurkin-kf2rr]

In my example the wild type and homozygous recessive have frequencies or amounts of 3 and 4 and my double crossover categories are 450 anf 460. I can only find examples with these same ratios as this video and never what I just postulated. Can you tell me what to do when you're parental is the smallest category and your double cross is the biggest? There are six total categories and I was told it was dropsophilia: a female heterozygous crossed with a male homozygous recessive.

[@youngsonmugode2859]

wonderful you are good tutor, i have understood clearly

[@jackiebrown4127]

Wow this makes so much more sense thank you

[@arnavbhavsar8567]

Thanks for making biology fun

[@nouraalq.6062]

thank you so much. Your video helped a lot!

[@erikdiaz8892]

Hey Joseph, what a great approach to explain how a genetic map is constructed. I'm currently constructing a genetic map for a 165-individual F2 mapping population. I wonder if you are interested in going beyond a conceptual approach and maybe use real data and R scripts to build an actual map. If so, I would be excited to collaborate! Cheers!

[@JosephRoss]

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

[@sushamaranisau8785]

Respected sir, you explain it so clearly, it helped me a lot. But at last part there is a small mistake. Recombination of A-B is 239 (as you write it) but B-C is total 261 and between A-C it is 482. Thus the gene order will be ABC. Kindly check it ...😊🙏

[@JosephRoss]

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 KZbin 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.

[@titoflash1212]

Thx, please keep making videos!!!

[@anuraghardi5365]

Hello !! I've a doubt. Now , we could use the cross gene genetics to get an animal hybrid .... So, could we use the cross gene genetics to get a human hybrid too?? Like if we cross the genes of a human and an lizard or an animal who has the ability to regrow its limb or a body part.... Can we get that into humans too after cross gene? If one has lost a leg or a hand....can he regenerate his leg/hand back as it was through cross gene!!

[@liam46800]

Great video!! Thank you!

[@rataneajbour2061]

شرح احسن من شرح مس

[@aadhavyasivakumaran5281]

Thank you so much!!!!!!!! Beautiful.

[@shrutidoshi9109]

So unique , thanx man 😇

[@syldin8638]

Aren't you forgetting the double cross-overs, from the B-C?

[@JosephRoss]

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!

[@Tommy2704]

Very helpful, thanks!

[@ablizrifat4307]

A2B2C1 should have A-B as non-recombinant since A B are both A2B2

[@JosephRoss]

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 KZbin had a better tool for me to point this out in the video itself!

[@alishaanand1988]

Hello sir have you made any videos on different types of models of crossing over?

[@JosephRoss]

No, I have not yet - thanks for the suggestion

[@alishaanand1988]

@@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 .🙏🙂

[@hgz11]

Just as an aside, is he writing in mirror image? How does this tech work? I have seen it quite a few times now.

[@JosephRoss]

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)

[@hgz11]

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

[@courtneyfaith1905]

What was the final order of the genes?

[@JosephRoss]

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)

[@Odin_valkiri]

@@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)

[@JosephRoss]

@@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.

[@seleepe6839]

What would happen if a situation was given like this and it was calculated exactly the way that you did it, but the result of the distance of 2 of the genes were >50 cM? Does it mean that this is a faulty situation or that there was a calculation error? Edit: To elaborate, one of the parental offspring populations was 6 (+,+,+) and the other was 4 (sb, bw, rm) out of 1000 total offspring.

[@JosephRoss]

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.

[@seleepe6839]

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

[@jhonraymundfernandez4215]

Isn't A-B and B-C = A-C? 🤔 since it is additive? Kindly enlighten me 😊

[@JosephRoss]

Interesting point. Yes, generally genetic distances are taught as being additive. However, there are always exceptions to rules, even in biology. There are a couple of factors that can influence additivity. One is that an assumption I made here (as stated in the video description) is that I'm not considering the possibility of multiple crossovers (which occur in reality and complicate the accurate calculation of genetic distance). Also, in reality (as opposed to an invented scenario for the purpose of instruction of the basic concept, as in this video) recombination events are not truly randomly distributed across chromosomes. The presence of so-called "recombination hotspots" can also influence additivity.

[@marshapple]

My professor could never explain this!

[@seandukes2109]

yesss left handed bio teacher

[@kmbeautyandmore4292]

why doesn’t crossing over occur in the F1 generation?

[@JosephRoss]

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.

[@kmbeautyandmore4292]

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

[@emvv3784]

15 minutes vs 4- 3 hour labs.

[@johnsontan345]

You're a godsend

[@poojajangir2910]

please someone tell me what kind of board it is??!!!!!

[@dandanthedandan7558]

Wait you're lecturing while writing backwards?!

[@JosephRoss]

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.

[@dandanthedandan7558]

Joseph Ross You, sir, are a genius.

[@krishthapar9929]

Excellent explanation! Though you couldve saved yourself a lot of work just by comparing dco versus parental to figure out the order

[@thepaddyg10]

thank you joseph

[@hadilballa6545]

thanks a lot that made it easier for me

[@Dia_in_a_daze]

Shouldn’t A be in the middle? B - C is 40 cm so if b were in the middle, a - c would be 40 + 20 which would make it wrong. I think a should be in the middle 🤯😵 I’m so confused

[@JosephRoss]

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!

[@Dia_in_a_daze]

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! 😊

[@Playstazn167]

Thank you so much!

[@brandoncashin8317]

Thanks really helpful!

[@D_panita]

Thank you sir!!

[@jekyll7110]

Bless you man

[@Ray-jg1bw]

Many thanks!

[@jantorkal6517]

awesome! am sorted!thankyou

[@shwetaparmar6742]

Thankyou really helpful

[@techheaven007]

very helpful.. almost saaved my life but distance between B-c is wrong i think.. that will be 21.75cM... total of ab+bc will be 41.66 where the standalone distance of ac will be 40.16... by subtraction we can now get the interference !

[@JosephRoss]

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.

[@hitkarshkushwaha2434]

YES techHeaven you are right

[@Shay-su6le]

@@JosephRoss ohhhhhhhhhhhh

[@rataneajbour2061]

شرح كثير حلو اتمنا النجاح

[@WILLIE8250]

Just a little math error, but explanation is on point

[@bausskilers]

thank you so much

[@brycesoraru9528]

Quite helpful.

[@pepperbox2282]

thank you kind sir

[@caseyhojecki4216]

bless you sir

[@fredrickasante3144]

Thank you

[@elrishiilustrado9592]

Thanks you!

[@MatthewBehling]

amazing

[@JuanGomez-tr7pq]

thanks dawg

[@kunukandayashodha2166]

need answers to your next time come to class questions

[@ritwikmandal1928]

U made a mistake b-c is 261R And a-c is 482 R

[@JosephRoss]

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.

[@russellkleiner2524]

king

[@Kevin-fv7hb]

whoa i was the hundreth like and this is the tenth comment

[@alishareeff818]

too confusing. Get better at teaching or don't teach at all.

[@mrpronerd]

Many thanks!!