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Genetic Recombination and Gene Mapping
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- Опубликовано: 14 авг 2024
- In this video Paul Andersen explains how the frequency of recombination between linked genes can be used to determine the relative location of genes on a chromosome. Thomas Hunt Morgan and Alfred Strutevant used the fruit fly to develop a theory of chromosomal inheritance and discover crossing over.
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All of the images are licensed under creative commons and public domain licensing:
"File:Drosophila Repleta Lateral.jpg." Wikipedia, the Free Encyclopedia. Accessed March 13, 2014. en.wikipedia.or....
"File:Morgan Crossover 1.jpg." Wikipedia, the Free Encyclopedia. Accessed March 13, 2014. en.wikipedia.or....
"File:Thomas Hunt Morgan.jpg." Wikipedia, the Free Encyclopedia. Accessed March 13, 2014. en.wikipedia.or....
"FlyBase," n.d. flybase.org/rep....
spax89. Illustration of a Tobacco Pipe, 2009. Extracted from Media:Blason de la ville de Saint-Quentin-la-Poterie (30).svg. commons.wikimed....
I swear these videos are 100% times better than the actual lectures from my university-run units. They should just show these.
I have done the majority of my learning on RUclips, for free and in half the time as in lecture. Yet I am paying enormous amounts of money for tuition. This is sad. The only redeeming quality of the school system that I can find is that it pressures me into learning the material for exams. If I didn't have that pressure, perhaps I wouldn't be bothered to learn the material.
funny you mention that cause we are mostly put on to watch his videos in my grade 12 Biology classes
A million times better than my lecturer!
Tom Parker def
Agreed. I've already learned more from him in a week than this entire semester.
I haven't watched Bozeman science since my senior year of HS AP biology class. Here I am, 5 years later in college watching him again. Thanks for getting me one degree and on the way to the second.
im in senior year ap bio right now lol. good luck on your next degree!
Exam tomorrow, and I now understand all of this. Bless your soul.
good luck! hope u did well back then
@@karinabuhaya5878 unfortunately he's not with us anymore because of this class
Same here
HELPFUL ? IT WAS WAS MORE THAN HELPFUL
trueee
The fact that i understand more about the whole chapter in this 10 minute video than my one and a half hour of lecture is amazing
It’s 1 AM the night before my AP bio exam, my bio teacher has spent the entire semester talking about her kids instead of teaching us, I want to thank you for being my bio teacher
Jo how did you do
We need to know, how'd it go
@@joebangles9951 got a three lol
@@Jo-gj2nr out of?
@@kurdweeb599 5, so not so bad
Mr. Anderson, Thank you so much for taking the time to post some of the most helpful science videos on youtube! Your time means the world!!
Dear Lord... i learned more in this video than in two lectures ...thank you
B to A should be 15 map units
+Whitaker Hoskins thanks i did pause and i couldnt figure it out...
+Whitaker Hoskins Realistically you are right but the recombinant frequencies come from a sample which means there is a range of error
Whitaker Hoskins why
Thanks I thought I was going crazy
so, when you look at the math behind the gene mapping, one would expect the distance from B-A and A-D to add up to the distance between B-D since A is just a point in between B and D. however, when you look at the numbers 30+25 does not equal 40. hope that helps
Just wanted to say thank you. I watched this video the night before my genetics exam because I was so confused and I scored 100% 😂🙌🏼
This video helped me a lot. I just have to consider some issues about the distance of B-A and A-D. Thinking of it mathematically the distance between B-D from the given data is equal to 55 map units which on that note it should be independently assorted.
It must have been 10 map units between A-D which would make total sense and the reordering of the gene map. I have to thank you Bozeman for letting us think critically and curiously
Your thinking is great, but in reality, his example is OK. It is possible (maybe even likely) there is a mistake and as a teacher he meant to give a simple example that added up nicely, but I think the numbers reveal the reality of genetic mapping.
At 8:57 he says "relative map distance", because recombination frequencies accurately tell the ORDER of genes on a chromosome relative to one another, but do not always accurately tell the exact DISTANCE. In other words, sometimes the math doesn't add up.
Reasons for numbers that don't add up are several. Double crossovers can result in incorrect distance calculations. Also, not all areas of the chromosome cross-over equally. Some areas are hotspots that have more recombination, and some areas like the centromeres have almost none. The farther apart genes are, the more opportunities there are for inaccuracy in distance calculations based on recombination frequency.
Side note: Another obvious reason the numbers don't always add up, though not related to this exact problem, is that some human chromosomes are 200+ map units. This method can only calculate up to 50 map units because recombination frequency can't go over 50%. Genes that are over 50 map units apart on a chromosome will all map as 50% RF. In such a case, we would need more genes to compare that are closer together, or modern gene sequencing techniques.
Also see Khan academy (bottom section of article): www.khanacademy.org/science/biology/classical-genetics/chromosomal-basis-of-genetics/a/linkage-mapping
@@joshuawhittaker1233 why cant the distance of the chromosome be higher than 50 map units and the recombination frequency between 2 genes must ne lower than 50% ? Not even exactly 50? Why if it's exactly 50, it means that the genes are in different chromosomes?
Blows off his homework. FIres up his pipe, and figures the whole thing out. Studivent was bad 2 the bone
I'm running out and buying a pipe. Maybe then I'll understand this. :-)
Sounds like me only i prefer a cigarette
Sounds like me right now except I’m just high af tryna study, all I’m saying tho, Alfred sparked the la
for the last gene mapping part. if B to C is 45%, isn't it impossible for A - B (30%) and A-D (25%) to be bigger than 45%?
A-B would be 15% right
agree
yeah I noticed that also
Ye...
i wish you well.7 years ago wow
I always use Bozeman science when I am stuck on something from a lecture at uni, helps me understand it in a better light and furthers my learning greatly.
Great video! Two comments. 1) 50% recombination doesn't necessarily imply the genes you're mapping are on different chromosomes. The could just be far apart on the same chromosome or have a recombination hot spot between them. 2) When you discuss recombination between the b and vg you have a green box labeled recombination and red boxes above and below labeled no recombination. I know what you mean but students may think that there is no recombination occurring in these regions. It may be but you just can't see it with the alleles you are tracking.
Thanks again for all your hard work making these videos. They are extremely helpful.
yes it does, as a chromatic only represent 50%, so if its more than this is means its not in the same chromatid and therefore chromosome after recombination
recombination is always checked pairwise, is it? Say, i want to find that final mapping of 4 genes a,b,c,d. So we do pairwise, taking 2 phenotypes at a time, and carefully choosing the corresponding flies?
I didnt understand ur second one
The problem you give at the end does not make sense. If the correct order is BADC, as you state, the distance between B-A that you list as 30 mu, and A-D you have listed as 25 mu combined give a combined distance of 55, which would signify that the genes B & D are probably not listed on the same chromosome, and no where near the listed 40 mu's apart. I think the distance between B-A was supposed to have read as 15, not 30, in which case the problem is correct, and the idea that there are 40 map units between B & D is sound.
Arjune Giri Amanda Shirley Maybe he wanted to give us an example of an anomaly of statistics and make us see that this idea still works.
+Amanda Shirley Or maybe he just made a mistake. It happens.
but I got BADC where A should be 10 units distant from D,here it is shown as 25!
noirrit nibedita no its 15mu
Total 50mu..longest b-c 45mu
So b-a + a-d + d-c (5%) = 45mu and on a 50mu chromosome
You can't combine the percentages. Assume they never relate in any way.
8:59 There's an issue now though because now B and A aren't 30% apart!
you get it! you have one the internet for today! congrats! hahah! holy cow what a mistake to have been made! omg, could never have been me!
Wouldn't the range between A & B be 15%? Because if B to D is 40%, subtracting A's 25% should only allow 15 units left over between A & B and not the 30% you have listed.
The only thing I'm going to remember after the AP exam: if you blow off your homework you might make a groundbreaking discovery.
Udy Kumra usohy
"and i hope that was helpful"
yes, yes it was! way more than the 2 hours i had in class today! thanks!! you're amazing!
I have my genetics exam tomorrow and this video has really help in thoroughly understanding Chromosomal Inheritance and recombination.
Vinaka
Fiji Islands
Mr.Bozemen you are truly godsent. I stg you a single-handedly getting me through college science at this point. I hope your pillow is always cold on both sides.
A-B is 15 m.u., not 30. Your sequence of B-A-D-C is right though. But thank you Mr. Anderson. You're an amazing teacher. I use your videos all the time to reinforce concepts in the minds of my AP Bio students. If only I had your talent!
In reality, his example is OK. It is possible (maybe even likely) there is a mistake and as a teacher he meant to give a simple example that added up nicely, but I think the numbers reveal the reality of genetic mapping.
At 8:57 he says "relative map distance", because recombination frequencies accurately tell the ORDER of genes on a chromosome relative to one another, but do not always accurately tell the exact DISTANCE. In other words, sometimes the math doesn't add up.
Reasons for numbers that don't add up are several. Double crossovers can result in incorrect distance calculations. Also, not all areas of the chromosome cross-over equally. Some areas are hotspots that have more recombination, and some areas like the centromeres have almost none. The farther apart genes are, the more opportunities there are for inaccuracy in distance calculations based on recombination frequency.
Side note: Another obvious reason the numbers don't always add up, though not related to this exact problem, is that some human chromosomes are 200+ map units. This method can only calculate up to 50 map units because recombination frequency can't go over 50%. Genes that are over 50 map units apart on a chromosome will all map as 50% RF. In such a case, we would need more genes to compare that are closer together, or modern gene sequencing techniques.
Also see Khan academy (bottom section of article): www.khanacademy.org/science/biology/classical-genetics/chromosomal-basis-of-genetics/a/linkage-mapping
I understand the concept better now, thank you! The only confusing part was the math in the RF example, the numbers don't add up.
OMFG I hope one day I can be as skilled as you to teach science, your videos are GOLD :D
I've taken a number of courses with this concept and did well enough on the tests, but it was only as I watched this video that it really began to truly make sense
The percentages of A-B + A-D = 55% or should I say 55 u.m.
Shouldn't = 40 % or u.m.?
As the distance from B-D (40%) ........since A is between them hmmmm
For someone like me. Besides reading the text book( which I don't get) to later watch a video.Your video helped give me a better image of whats been spoken about in class.Thank you.
I was going over my lecture material for like an hour and was stuck on the recombination frequencies, I'd almost lost all hope until I found this video. You explained it all so well I can finally understand it now, thanks!
most pedagogic teacher ever, awesome video
you and the amoeba sisters have helped me out a lot this semester
This less than 10 minute video just helped me understand what my teacher tried to teach me in a 1.5 hour lecture.
THOSE VIDEOS HAVE ACTUALLY HELPED ME UNDERSTAND AT ONCE ALL THE THINGS MY UNIVERSITY TEACHERS FAILED TO EXPLAIN CLEARLY! THANK YOU SO MUCH!
I am so thankful I stumbled upon your channel, this video in particular. My praxis biology content exam is coming up and your videos are a blessing!
You made me understand in 10 minutes what my professor couldn't over 2 weeks
This is super helpful great job Mr Andersen! Sincerely student trying to pass HL bio
Thank you Professor.You make things really simple and easy to understand.
Don't know what I would have done without your videos and Khan academy this quarter! Thank youuuu!
Hey Paul, I noticed at 9:06 that A was placed closer to B when it should be closer to D. Great video by the way, helped a lot!
Actually just saved my life. You made a hard concept easy to grasp for anyone. Thanks!
UC honors bio genetics class. Lectures didn't explain this and textbook didn't bother to explain either. You're my go-to source for bio videos
Sir you are the best teacher for genetics i would say.. Your vedios have helped me a lot. Thank you so much.
*videos
I was confused by my teacher’s lecture today but now I understand the topic!
Explanation was crystal clear, understood the concept. Thanks Paul. Kudos
You are such a great instructor. The visuals were so helpful as well. Thank you!!
Man, this guy looks like Hank Green, and he lives in Montana also
+Jim Gibbs
He is way better looking than Hank Green
There related
jk idk
Tinuviel 19715 oooooofff
it's very helpful. Now I am prepared for my test tomorrow. Thanks
Mr. Anderson is my lifesaver every time 🙌🏻🙌🏻
Excellent video, very helpful. I never understood gene mapping until I watched this video. Thanks so much 🙏❤️💕
whats life without paul andersen... thank u paul ^^
A and B should be 15 cM apart, not 30 cM
I agree that A and B should only be 15 map units apart. Otherwise A--> + B--> is greater than 50. Please add a text note to the video.
yeah makes sence, so that B---A---D---C add up to 15+25+5=45 which is the distance between B---C
actually they are probability, not actual measurements
satinderjit4 , you are correct that they are measured in probability. A 'cM' is a centimorgan which corresponds to 1% probability.
Levi Marshall, I had the same thought as you had at first that they were actual measurements and not probability so I spent my time trying to group the genes together so they would total the largest distance. It's nice to know, this is a lot easier than that.
I was so confused in the lecture, this video has helped me so much, all your videos explain perfectly! Thank you very much!
Damn. Mr Anderson, you make some of the trickier aspects of my degree so easy to learn. Your videos are an asset to my learning. Thank you. And to answer your question. Yes. It was helpful 👍👍
Really awesome work
would u mind if i take few snapshots and use it for my class ?
thank you
ive been watching these videos since 11th grade AP bio and they're even helping me now in my 2nd year in undergrad :')
I guess studying at one of best university in the world doesn’t necessarily mean you have access to one of the best teachers in the world . Thank you for this
regarding the problem, I think the distance between A & C is 25% not between A & D.
think youu
This was so helpful! I love that you actually used an example och how to solve it
All excellent teachers should be required by law to make youtube videos :D Thank you for your time Mr Andersen, your contribution is invaluable!
Amazing video! Explained it in a way that was easy to understand and had excellent visuals to match. Keep more videos coming!
my HS teachers traumatized me by making us watch you all the time but I'm so glad I got over it! woohoo ty very helpful
thanks so much
what I admire about you lessons that they are deep and focus on the historical background and how did they figure out the thing you are explaining rather than just memorizing without understanding the origin
why exactly arent u teaching at a top rated university ? my genetics prof. is the worst instructor anyone could have!! THANK YOU FOR THE VIDEOS!
Very helpful, thank you so much. 1000% times better than my college professors could explain over the course of several lectures.
super helpful. I watch all your videos for uni. cheers
you are the uni lecturer we need but don't deserve
You just saved my grade for finals. Bless your soul.
i love your videos so much, it gives me hope, I've been watching them since my freshman year now I'm a junior taking genetics, you helped me through BIO1 and 2 now i feel confident about genetics.
-Thank you
As soon as he said "Mr. Anderson" i thought of: "It's inevitable... Mr. Anderson...".
You explain so many different topics well!
Given the conceptual problem on map units, I think the A-B and A-D distances must be reversed( by moving the A unit slightly to the right) the distance between A-B should be slightly larger than the distance between A-D and in the illustration it is not looking that way
A small doubt.....
if the frequency of recombination of genes A - B is like >~40%, then the genes might be on the two different sides of the centromere (in a metacentric chromosome), right?
Then during meiosis, the two genes (A, B) might be crossed over as it is to the other homologous chromosome(as crossing overs take place on different sides of the centromere), right?
Then the frequency of recombination of two genes A, B might fall down (and eventually the genes come closer???)?
Did I get the whole concept wrong or did I miss any important thing??
We watch your videos in IB Bio HL, and they help a ton! Thanks so much!
Well done dear contributor Paul Andersen!
Great video. Quick question though: in the example shouldn't A be closer to D than to B? This is because the recombination frequency between B and A is 30% while the frequency between A and D is 25%. The closer they are the smaller the frequency right?
I was about to comment on the same thing. I was gonna have my students do this problem, but I thought A would be closer to D also, just a bit to the right of the halfway point between B and D.
Just in time for my final next week! Thank you so much, I owe my A in Bio this semester to you! :)
This is how you properly explain Genetic Recombination and Mapping. By watching this, I was able to FULLY understand it!! Bye Universities. LOL
very well explained, thank you Mr. Bozeman
Thank you sooo much, my teacher never really covered recombination mapping and I really appreciate the help!!
Who's here during COVID and acting like they're getting an education through online classes but have to resort to channels like Bozeman?
Thankyou for this! You're infinitely more helpful than the so called "teaching academics" at my university.
You are a great teacher and speaker! Thanks for the videos!
In the first example, since the genes were linked(found on the same chromosome) then shouldn't the theoretical gametes of the heterozygous drosophila just be vg+ b+ and vg b. Therefore, the offspring is theoretically expected to be 50% wild type and 50% mutant. However, what happened instead was that there was a percentage of mutants that had one were wild type for wings but mutant for bodies and vice versa.
That would then be thought of as a result of crossing over, which according to your data is 17%.
I was thrown off because the mutants were already expected when I think I read in a book that seeing the mutants that were mutant in one gene but wild type in the other actually threw Morgan a bit off.
Thank you so much! This illustration and connection is EXACTLY what I was looking for!
Wow. What a crystal clear explanation. This is beauty.
Thank you so much.
Thank you.
This helped me a lot!!!
After watching Nth number of video on this. Finally I landed on this!!!! And it cleared all my doubt. I feel like I have attained enlightenment. Thank you so much sir
My professor said that the recombinations frequency of vg-cn is 9.5%
The gene mapping at the end of the video is wrong as the distance of A-B is bigger than A-D so should be closer to D than B.
Way better than my crappy genetics teacher at school. Thank you!
so the recombination frequency percent basically represents the distance between the two genes? the higher the percent the further apart the genes are and the less likely they will cross over and exchange dna/genes w/ their homologous partner?
I really enjoy your lectures.. In fact I am looking for them
i feel bad for those fruit flies, everytime i make them in my green box i just put it outside and set them free
Making dummies like me smarter thanks this really helped me out for my genetics class.
Well explained and very nice video. However, the gene maping exercise was a bit confusing for me. The B-C is mentioned as 45% in the question, but while maping in the chromose, it seems to be greater than 45.
Thank you Paul! I was looking for an explanation like this one! Great work thanks again :)
Thank you So much KDB... Assisting on and off the Pitch
bless you. this was so much easier to follow than an hour long lecture
Thanks a lot Mr.Anderson,I cud finally figure tht out!!It wasn't so tough aftr all...:)
Just one doubt,in the exercise tht u gave,shouldn't A be more close to D than B as AD is 25 centimorgan and AB 30 centimorgan?
Thanks again!
Thanks Mr. Anderson!!!! Your videos always help me!!
thanku sir this video was more helpful than the schools lecture