this was the BEST video I've ever watched on pedigrees. I literally felt my stomach drop as a reaction to so suddenly (and FINALLY) understanding something.
This method is simply brilliant. When this was first introduced in class, I solved the pedigree in a mere 10 seconds while the rest of the class was struggling. thank you for your amazing work :)
Sure - this way gets to the same answer, faster. But it is quite possible that a student could solve the pedigree using this method without really understanding the genetics behind the solution. Then if they are asked questions such as "what evidence in the pedigree excludes X-linked recessive as a mode of inheritance?" they will say something that is just about pattern-matching, rather than giving a *genetic* explanation - in terms of alleles and inheritance. I think as long as you understand the other technique, this shortcut is perfectly fine as a tool ... it's what I use whenever I need to analyse a pedigree. Just make sure you understand why, for example, a recessive trait must be inherited by the sons of a woman with a recessive X-linked trait. Then use it with confidence :)
This excellent proposal for a quick and simple analysis of a pedigree has two possible pitfall for both questions. For the first one, it is possible a dominant inheritance with incomplete penetrance. For the second one, the classical division of X-linked inheritance between dominant and recessive patterns is now overcome and the women's phenotype depends on the proportion of cells with inactivation of the mutated X chromosome.
This helped me soo much. I have a test tomorrow and I don't want to flunk it because I didn't understand my taecher. Most of my work i get ,but the other day I totally zoned out. Thanks so much
This might sound silly but at 1:32, you talk about answering your question one of the two questions we need to ask to solve this. If the parents are dominant, doesn't that mean both the children will be affected? How exactly does the child being recessive equals the parents being dominant? Additionally, if the parents are dominant why are they not shaded in to show they are affected? I don't know why but for me particularly this is a major source of confusion. Would really appreciate a reply that clears my confusion on these matters. Thank you
+HamadKadventures the child having the recessive trait, equals the parents having the dominant trait, because she is shaded and they are not. There are two traits: 'affected' and 'not affected'. If we are able to show that one of those traits is recessive then anyone with the other trait must logically have the dominant trait. In this case, we are able to show that the daughter has the recessive trait, so therefore (since her parents have the other phenotype) they must have the dominant trait. It is a bit like saying that if we can prove that a coin fell heads up, then it must have fallen tails down. If shaded is recessive, then not-shaded is dominant. Shading does not show whether they have the dominant trait or not. It shows whether they are affected by whatever genetic disorder we are discussing. In this case the genetic disorder is recessive, so those individuals who do not express the disorder are not shaded - and they have the dominant (not affected) trait. I hope that clears a few things up for you.
Andrew Douch Hello Andrew, thank you so very much for the comprehensive reply. I completely understand. I think my confusion came from a lack of understanding of the terminology and massive lack of sleep haha. I have to say I absolutely love your videos and I can't thank you enough for them, thank you!!! Trying to cover as much ground before the GAMSAT exam, this really helped. :)
if it's not possible to resolve a mode of inheritance from the available data using this method then it would also not be possible using another method. Sometimes a pedigree does not contain enough information to be able to conclusively determine the mode of inheritance
I've learned more about how to solve pedigrees and why in this video than in the hours and hours I've spent studying. Thanks, I really needed help understanding these f%&*@(% things. ^_^
An even faster method is just by looking at the parents and progeny. If progeny is affected and parents are unaffected then it is always AR inheritance and also consider these situations. aa X Aa ( mom on left side and father on right side) will always give AD inheritance and swap their positions it will give AR inheritance. I also confirmed it with your previous videos. It always works
The question you need to ask yourself is not whether a pattern exists - but whether there is any genetic basis for thinking that it should. If a trait is autosomal, then aa x Aa is no different to Aa x aa. Any such pattern you have observed must be coincidental.
+Andrew Douch Yes it is a coincidence and a very good one I must say. Your video was about quick methods to do pedigrees and this is one really quick way if you literally have just 10-20 seconds to do it. And this is foolproof I know because I have used them in my entrance exams and got them correct as well. Missed the medical seat by 2 marks is a different story. But keeping that aside what I said works just fine too
This is really helpful, thank you. But what if it is a "no" to the first question? Does it mean that I have to go through the long way instead of using this shortcut?
+Calvin Chan It won't make any difference. If there is insufficient data to determine the mode of inheritance using this method, then the long method will also show that there is more than one possible mode of inheritance.
Thank you very much for the tips on the video! I'm also a little confused, is it possible to consider the penetrance? Can this also be an autosomal dominant pattern with incomplete penetrance in subject #5?
A recessive phenotype is a phenotype that is only expressed if the individual is homozygous. The dominant phenotype is expressed if there is even one allele for it in the genotype. Another way of thinking about it is that the phenotype of a heterozygote (Eg. Bb), is the dominant phenotype.
Andrew Douch hey mate-- what happens if the pedigree doesnt have a child whos phenotype is different to both his parents?-- do u just have to use the long method?
... if that's the case (in the absence of other information) then the pedigree doesn't provide enough evidence to be conclusive. If you used the long method, you will also find that it's inconclusive.
I tried to apply this rules in about 50 pedigree questions. 40 were correct but i have 10 questions where this rules doesn't apply. Tell me a way to send you those questions.. This trick is wrong
It's not really a trick. it's just a quick way of applying the rules/patterns that underpin a pedigree. it always works if you use it correctly. I've seen students use this process but use it incorrectly. For example answer yes to question 1, when the answer was in fact no. On the other hand if you find a pedigree that this process doesn't work for, then I'm confident that pedigree can't be solved using any method, either - perhaps there is not enough evidence in the pedigree for it to be solved, or there is some other weird thing (in an actual family this may be because a child is not truly the child of a man, even though history records it as such). But assuming the pedigree can be solved using any other method, then it can also be solved using this.
4:57 Don't want to be this person that says the ''Um, actually'' but I fear I must: Um, actually that is not true of all boys because not all boys have XY chromosomes, the thing that determine your chromosomal sex is the presence or lack of the SRY gene, now typically the SRY gene is placed on the Y chromosome but it is far from rare that the SRY gene would ''hop off'' and change it's locus to a X chromosome, causing a boy with XX chromosomes to be born
You are not wrong but "far from rare"? De la Chapelle syndrome (which you are talking about) results from a translocation mutation, and affects just 1/20,000 baby boys (for comparison Turners Syndrome affects 1/2,000 girls and Klinefelter's affects 1/650 boys). So it is, in fact, statistically *very* rare. Besides, you can find an exception to almost anything in Biology if you try. The purpose of this video is to explain how to methodically interpret a pedigree. Confusing that by including rare exceptions would not be helpful. There's certainly a time for learning about translocations, aneuploidy and other exceptions - but an introductory video about pedigree analysis is not that time. (besides if you want to get technical, even saying that sex is purely determined by the presence of the SRY gene somewhat simplistic) - but again, the point of this video was not a deep dive into sex determination, but a how-to video, teaching a systematic approach to interpreting a pedigree - and it will produce an accurate result in 19,999/20,000 cases. ;)
@Andrew Douch ‘’besides if you want to get technical, even saying that sex is purely determined by the presence of the SRY gene somwhat simplistic’’ I fully agree with that statement and you are right that a seven minute video is not the time to unpack the complicated endocrinological, genetic and chromosomal mechanisms of sex. But I do believe that if you are fully aware that XY or XX is not what makes someone a male or a female it is unnecessary (and may lead people who are watching this video to hold a misconception about sex) to put that strong of an emphasis on the matter P.S. I would also recommend to use the terms male/female or man/woman when talking about biology because the words boy and girl have become more connected with gender than with sex in the past couple of years.
That's not right at all. The shaded individuals are the ones that possess whatever phenotypic trait you are investigating. If the pedigree shows a family with cystic fibrosis, then those individuals that suffer from cystic fibrosis will be shaded - yet cystic fibrosis is a recessive trait.
Dear sir, q. no. 1 "Is there anyone whose phenotype is different to that of both their parents?" if the pedigree shows such kind of pattern you are saying that it should be recessive. But this statement is rediculous !!! I will give you a condition - Mother is having autosomal dominant(heterozygous) disease and father is also having the same situation. But their children did not get any disease because all the children got the non disease causing allele (recessive one) from both the parents. Then this leads to a condition that their children are phenotypically different from both their parents( parents have disease and children not having a disease). Then your statement will be wrong!!!!! please explain...
You have misunderstood, Dinesh. Taking the situation you have described, the answer to the first question is "Yes, the children have a phenotype different to both their parents" Therefore, (according to my process) those same children must have the recessive trait. And if they have the recessive trait then their parents must have the dominant phenotype. Look at example 2. It describes exactly the scenario you have described. th-cam.com/video/svtHWJdQYOk/w-d-xo.html
this was the BEST video I've ever watched on pedigrees. I literally felt my stomach drop as a reaction to so suddenly (and FINALLY) understanding something.
exactly!
Helpppp meeeeee
i cant thank you enough i have exams tomorrow and this just boosted my confident a million time
keep it up
This is coming all the way from the U.S.A., thank you so much! You are a true life saver!
This method is simply brilliant. When this was first introduced in class, I solved the pedigree in a mere 10 seconds while the rest of the class was struggling. thank you for your amazing work :)
Not only have you taught me a useful trick, you made me understand the concept of sex-linked trait
Okay, sir... you are now the best person ever. Went from being completely confused about this topic to :D
This saved me
I have a test in 3 hours and this is one of the major things I needed to clear things up. Thanks a bunch! :)
You are a good man
This is by far the best explanation I've seen. So many thanks!
exam on monday its time for an Andrew Douch marathon! Excellent Job!
loved it!!!! I have a test in 2.5 hours and this saved my butt!
Sure - this way gets to the same answer, faster. But it is quite possible that a student could solve the pedigree using this method without really understanding the genetics behind the solution. Then if they are asked questions such as "what evidence in the pedigree excludes X-linked recessive as a mode of inheritance?" they will say something that is just about pattern-matching, rather than giving a *genetic* explanation - in terms of alleles and inheritance. I think as long as you understand the other technique, this shortcut is perfectly fine as a tool ... it's what I use whenever I need to analyse a pedigree. Just make sure you understand why, for example, a recessive trait must be inherited by the sons of a woman with a recessive X-linked trait. Then use it with confidence :)
Andrew Douch Sis, are you a Geneticist?
This excellent proposal for a quick and simple analysis of a pedigree has two possible pitfall for both questions. For the first one, it is possible a dominant inheritance with incomplete penetrance. For the second one, the classical division of X-linked inheritance between dominant and recessive patterns is now overcome and the women's phenotype depends on the proportion of cells with inactivation of the mutated X chromosome.
This helped me soo much. I have a test tomorrow and I don't want to flunk it because I didn't understand my taecher. Most of my work i get ,but the other day I totally zoned out. Thanks so much
I really wish someone had explained the same way earlier ! you r the best sir ! the best explanation i could have found for the pedigree is this 😇😄
YOU SIR ARE AWESOME
Please post a link in the video description to the other video you refer to in this this video (0:36). Thanks for a great video!
Great Videos Sir!
Now I can solve pedigrees in few seconds. Credit goes only to you! You're the Best....
Subscribed!
I needed to brush up on pedigrees. Thank you for such a helpful video!
This might sound silly but at 1:32, you talk about answering your question one of the two questions we need to ask to solve this. If the parents are dominant, doesn't that mean both the children will be affected? How exactly does the child being recessive equals the parents being dominant? Additionally, if the parents are dominant why are they not shaded in to show they are affected? I don't know why but for me particularly this is a major source of confusion. Would really appreciate a reply that clears my confusion on these matters. Thank you
+HamadKadventures the child having the recessive trait, equals the parents having the dominant trait, because she is shaded and they are not. There are two traits: 'affected' and 'not affected'. If we are able to show that one of those traits is recessive then anyone with the other trait must logically have the dominant trait. In this case, we are able to show that the daughter has the recessive trait, so therefore (since her parents have the other phenotype) they must have the dominant trait. It is a bit like saying that if we can prove that a coin fell heads up, then it must have fallen tails down. If shaded is recessive, then not-shaded is dominant. Shading does not show whether they have the dominant trait or not. It shows whether they are affected by whatever genetic disorder we are discussing. In this case the genetic disorder is recessive, so those individuals who do not express the disorder are not shaded - and they have the dominant (not affected) trait. I hope that clears a few things up for you.
Andrew Douch Hello Andrew, thank you so very much for the comprehensive reply. I completely understand. I think my confusion came from a lack of understanding of the terminology and massive lack of sleep haha. I have to say I absolutely love your videos and I can't thank you enough for them, thank you!!! Trying to cover as much ground before the GAMSAT exam, this really helped. :)
thank you very very very very much sir ....you have changed the way i thought about pedigrees.....
upvoted. thanks so much for the help Andrew
if it's not possible to resolve a mode of inheritance from the available data using this method then it would also not be possible using another method. Sometimes a pedigree does not contain enough information to be able to conclusively determine the mode of inheritance
omg thank you!!!!!! you are a genetics angel
Amazing video! Keep it up!!
Thank you so much!!!!!! Have my medical finals in a week, this really helped :)
Love the way you explained this--very helpful!!!
I've learned more about how to solve pedigrees and why in this video than in the hours and hours I've spent studying. Thanks, I really needed help understanding these f%&*@(% things. ^_^
Incredible
You just saved my life.
This cleared up so much confusion! Thanks. :)
Very Clear and nice explanation!
An even faster method is just by looking at the parents and progeny. If progeny is affected and parents are unaffected then it is always AR inheritance and also consider these situations. aa X Aa ( mom on left side and father on right side) will always give AD inheritance and swap their positions it will give AR inheritance. I also confirmed it with your previous videos. It always works
The question you need to ask yourself is not whether a pattern exists - but whether there is any genetic basis for thinking that it should. If a trait is autosomal, then aa x Aa is no different to Aa x aa. Any such pattern you have observed must be coincidental.
+Andrew Douch Yes it is a coincidence and a very good one I must say. Your video was about quick methods to do pedigrees and this is one really quick way if you literally have just 10-20 seconds to do it. And this is foolproof I know because I have used them in my entrance exams and got them correct as well. Missed the medical seat by 2 marks is a different story. But keeping that aside what I said works just fine too
+Andrew Douch and btw I loved your 4 hypothesis method too. Works like a charm
You're amazing, thank you so much!
omg i get it spent so long looking for a good tutorial
This is really helpful, thank you. But what if it is a "no" to the first question? Does it mean that I have to go through the long way instead of using this shortcut?
+Calvin Chan It won't make any difference. If there is insufficient data to determine the mode of inheritance using this method, then the long method will also show that there is more than one possible mode of inheritance.
You say the other method is better, but this method is absolutely fine isnt it? Why would I bother to do the slow way? Just as a double check?
It was actually very helpful...
Thank you Sir.....
You saved us! Thanks for the help!
Finals tomorrow! thanks so much!!
Thank you very much for the tips on the video! I'm also a little confused, is it possible to consider the penetrance? Can this also be an autosomal dominant pattern with incomplete penetrance in subject #5?
And im back to review the best video on this!
thank you so much..this method is easy to understand thanks
you are A GENIUS THANK YOU SOOOOOO MUCH ❤
Very easy to understand
Where were you for the MCAT lol
+Sixtown13 LMAO I feel you. Time is $$ on the MCAT.
What do you mean by recessive phenotype and Dominant phenotype?
A recessive phenotype is a phenotype that is only expressed if the individual is homozygous. The dominant phenotype is expressed if there is even one allele for it in the genotype. Another way of thinking about it is that the phenotype of a heterozygote (Eg. Bb), is the dominant phenotype.
soo good explained!!
This is awesome!
Sir can't we also say that it isn't X-linked as there is no girl affected in the P1 generation?
Andrew Douch hey mate-- what happens if the pedigree doesnt have a child whos phenotype is different to both his parents?-- do u just have to use the long method?
... if that's the case (in the absence of other information) then the pedigree doesn't provide enough evidence to be conclusive. If you used the long method, you will also find that it's inconclusive.
ok thanks
Sir, I'm not able to find d 4 hypothesis method pedigree analysis in ur channel?????
+Hari sinchan I know it is very late, but I am answering to help other people. The 4 hypothesis method videos are his "Pedigree Analysis" videos.
+mirrorreflex Thanks mirorreflex. :)
good stuff man this helps
7 years after it I’m watching it
Same
Its the failure of schools not teaching tricks like this that prevent more people from understanding science.
So what happens if there are no daughters that are recessive?
It was really helpful!
SO HELPFUL
nice explanation.
I tried to apply this rules in about 50 pedigree questions. 40 were correct but i have 10 questions where this rules doesn't apply. Tell me a way to send you those questions.. This trick is wrong
It's not really a trick. it's just a quick way of applying the rules/patterns that underpin a pedigree. it always works if you use it correctly. I've seen students use this process but use it incorrectly. For example answer yes to question 1, when the answer was in fact no. On the other hand if you find a pedigree that this process doesn't work for, then I'm confident that pedigree can't be solved using any method, either - perhaps there is not enough evidence in the pedigree for it to be solved, or there is some other weird thing (in an actual family this may be because a child is not truly the child of a man, even though history records it as such). But assuming the pedigree can be solved using any other method, then it can also be solved using this.
Thanks! So helpful
I used this method for solving some pedigrees but got two pedigrees incorrect. Am I allowed to e-mail you?
+Rebecca Chen sure :)
+Andrew Douch actually i figured it out!! wish me luck on my midterm thats happening in ten minutes!! thank you for your videos on pedigrees!!!!!
Test tomorrow, thanks :)
thank you, sir!
Thank you so much 😍
really really helpful... Thx
Thank you sir
wow thank you so much!
what if theres a diamond signifying multiple children?
Awesome 🎉
thanks a lot bro .. bio paper in 4 hrs
I still don’t get it 😭
4:57
Don't want to be this person that says the ''Um, actually'' but I fear I must:
Um, actually that is not true of all boys because not all boys have XY chromosomes, the thing that determine your chromosomal sex is the presence or lack of the SRY gene, now typically the SRY gene is placed on the Y chromosome but it is far from rare that the SRY gene would ''hop off'' and change it's locus to a X chromosome, causing a boy with XX chromosomes to be born
You are not wrong but "far from rare"? De la Chapelle syndrome (which you are talking about) results from a translocation mutation, and affects just 1/20,000 baby boys (for comparison Turners Syndrome affects 1/2,000 girls and Klinefelter's affects 1/650 boys). So it is, in fact, statistically *very* rare. Besides, you can find an exception to almost anything in Biology if you try. The purpose of this video is to explain how to methodically interpret a pedigree. Confusing that by including rare exceptions would not be helpful. There's certainly a time for learning about translocations, aneuploidy and other exceptions - but an introductory video about pedigree analysis is not that time. (besides if you want to get technical, even saying that sex is purely determined by the presence of the SRY gene somewhat simplistic) - but again, the point of this video was not a deep dive into sex determination, but a how-to video, teaching a systematic approach to interpreting a pedigree - and it will produce an accurate result in 19,999/20,000 cases. ;)
@Andrew Douch
‘’besides if you want to get technical, even saying that sex is purely determined by the presence of the SRY gene somwhat simplistic’’
I fully agree with that statement and you are right that a seven minute video is not the time to unpack the complicated endocrinological, genetic and chromosomal mechanisms of sex.
But I do believe that if you are fully aware that XY or XX is not what makes someone a male or a female it is unnecessary (and may lead people who are watching this video to hold a misconception about sex) to put that strong of an emphasis on the matter
P.S. I would also recommend to use the terms male/female or man/woman when talking about biology because the words boy and girl have become more connected with gender than with sex in the past couple of years.
Omi it’s my edrolo teacher
same
Ty for the vid
GOD TIER VIDEO
superb!! tysm!!!
thanks!
great man
thanks
thank you :)
The dominant gene is always shaded and yours isn't. Very confused now.
That's not right at all. The shaded individuals are the ones that possess whatever phenotypic trait you are investigating. If the pedigree shows a family with cystic fibrosis, then those individuals that suffer from cystic fibrosis will be shaded - yet cystic fibrosis is a recessive trait.
nice feeling huh? ;-)
Dear sir, q. no. 1 "Is there anyone whose phenotype is different to that of both their parents?" if the pedigree shows such kind of pattern you are saying that it should be recessive. But this statement is rediculous !!!
I will give you a condition - Mother is having autosomal dominant(heterozygous) disease and father is also having the same situation. But their children did not get any disease because all the children got the non disease causing allele (recessive one) from both the parents. Then this leads to a condition that their children are phenotypically different from both their parents( parents have disease and children not having a disease). Then your statement will be wrong!!!!! please explain...
You have misunderstood, Dinesh. Taking the situation you have described, the answer to the first question is "Yes, the children have a phenotype different to both their parents" Therefore, (according to my process) those same children must have the recessive trait. And if they have the recessive trait then their parents must have the dominant phenotype. Look at example 2. It describes exactly the scenario you have described. th-cam.com/video/svtHWJdQYOk/w-d-xo.html
superb (:
wowwwwwwwww thank you sir
the bestt
I got lost at 3:30 omg
AD with incomplete penetrance
What if there are no girls and it is only male?
I love you
No homo
ححح
ggg