Pedigree Analysis methods - dominant, recessive and x linked pedigree

[Music] hello friends welcome to another video tutorial from shamans biology and this video lecture I will be talking about pedigree analysis and I already recorded some video regarding how to find out whether the pedigree is dominant recessive or autosomal or x-linked you can watch that video anytime but this video is going to be an overview of all those different pedigree types how to find out them and then how to solve some examples of pedigree analysis so let's start with it before understanding of pedigree analysis you should know what is pedigree pedigree is a representation of a family tree or family history of diseases that we usually analyze based on how those diseases are transferred from their parents to the next generations and offsprings now if you look at those charts it is going to give us an idea about the way the disease transferred and the type of the transfer of the disease that are known as inheritance inheritance patterns okay and that there are four types of inheritance patterns possible based on first is based on whether the gene that is being transferred is dominant or recessive or whether the gene is present in the autosomal chromosome or in the sixth chromosome or X chromosome okay now you know that let's say we are talking about a disease and the disease here we are talking about the gene a is causing a disease now capital a is the dominant form so if the gene is present as capital A it is causing the disease okay so now the disease could be two type it could be dominant format or recessive type it could be autosomal that means this disease gene is carried by a body cell chromosome or extra length that as this gene should can be present in the X chromosome of our body x and y are the two sex chromosomes of our body which is different than the autosomes which are 22 pairs okay so now all the varieties of this disease and inheritance patterns could be represented by the combination of this four types so let us look at them first it could be dominant autosomal so we call it autosomal dominant second one autosomal with recessive type so carried by the autosomes an autosomal chromosomes but it is in recessive format third one is x-linked dominant so present in the X chromosome but the disease is a dominant type fourth one x-linked recessive when it is also carried in the X chromosome but it is in recessive format so if four types of disease inheritance patterns that are possible for any of the pedigree that we got in their exams and times to provide to answer we will check for all these four types to find out which among this four is best fit for that pedigree to explain so let us look at examples so there are certain rules to find out the type of pedigree that we usually know first is the autosomal dominant for the autosomal dominant type of pedigree there are some rules to find out how autosomal dominant disorders affect children usually have affected parent so if your father is affected you should be affected that is the idea of autosomal dominant that means you will never see two partners none of them had the disease but suddenly one of their offspring get the disease for autosomal trade this will not happen affected children usually should have affected parent okay now to effective parent can produce unaffected child so it might happen that two affected parents can have effective child this thing is possible for autosomal dominant okay two unaffected parent will never have affected children this should never happen for an autosomal trait autosomal dominant predatory so for autosomal dominant what you should find out is that why it is an autosomal trade you will find out that this disease should be spread across the male as well as female populations almost equally okay that is the biggest example of autosomal trade while x-linked rates usually tend to be more towards the male populations so males are much prone to get the x-linked diseases compared to the female because they have only one x chromosome now this is the thing that I want you to remember so two parents affected none of the children affected two parents unaffected the children affected it is not possible so if this scenario originates it means it is a recessive disease if this occurs it is a dominant disease okay so let me erase let us go to the second type which is autosomal recessive pedigree chart in the autosomal recessive disorders most of the affected children have their most of the affected children do not have any affected parent see most of the affected children have normal parents so normal parents will give rise to affected children this is known as this is a part of recessive type of trait and if it is a recessive trait it will not show up in every generation it can skip generations that is the ultimate idea of recessive trait it will not show up every time as you see this is the generation where you have the trait shown in the next generations no traits are shown and again afterwards in another generation it is shown again okay and as it is autosomal it means both males and females are affected with equal frequency the third type is the x-linked recessive pedigree x-linked pedigree means it is mostly affecting males and importantly x-linked recessive pedigree x-linked recessive diseases affect more males compared to the females so in a population you will see most of the males are getting the disease as it is recessive it can skip generations another important thing is that this disease is transferred from the mother to son okay the fourth type is the x-linked dominant pedigree x-linked dominant pedigree is again if a father is affected then all the daughters will be affected but in x-linked recessive pedigree this trait we never transfer from father to son it will never transfer x-linked recessive disease always transfer from mother to son father to daughter now x-linked dominant if father is affected all their daughters will be affected because if father is affected it has only one x and the the chromosome that father supplies to the daughter is that X so if father is affected that means that if X is affected it is going to give that X to the daughter and if it is dominant in nature so it is going to express the disease right so these are the different rules and ideas to how to actually get a pedigree by looking at it but again all these methods are not always foolproof because if you see a pedigree for a small area that can be explained by one or multiple type of traits like multiple type of inheritance patterns can fit to explain that pedigree as well this type of situations may originate but for releasing that idea and for for actually releasing all those complications you need to look as far as you can for a pedigree to analyze as back as you can through the track of the family history and as back as you go as more people will be involved and the pedigree becomes larger and bigger you are getting more closer to find out the right type of inheritance for any gene or any disease gene or any other gene that we are looking for okay so now we will solve some sort of pedigree related problems you solve this one as you see here we see here in this looking at this pedigree that this disease this black shade means they have a diseased gene that this is gene is present both in men as well as in female so it is well distributed we see another thing that in third generation mother father not affected mother and father and none of their children are affected it's good if one of them affected is going to transfer it so the idea if you look at very clearly we see every generation has the disease if there is a disease organism desist individual it is transferring the disease it is not skipping generations so it is mostly dominant type another thing that this disease is well distributed between male and female both so it is not excellent it is autosomal so we can say this is an autosomal dominant trait okay now let us say whether we can explain this trait with autosomal dominant feature so autosomal dominant means let us say a is the disease gene so if capital e capital represent it means disease if capital is smaller present it also means disease the only way disease is not there if it have the genotype small a small e so look at here in the first case it could be either capital a capital A or capital is smaller this one could be capital a capital or capital is smaller now as you look at the offsprings one of them did not get the disease so this is the indication to affected parents but the child is not having the disease the only way it is possible if the trait is autosomal dominant if it is autosomal recessive then obviously this child is going to get the disease okay so that is why it is a full proof that this trait is dominant autosomal so if we look at here it should be small a small way to not get the disease so as it is getting too small a that means both of their parents should have at least one small age so we are sure that both the parents contain capital a small a genotype okay now let us say okay half like that now as we have small a small a this one also small a small in all the springs are small a small a so we are explaining this whole pedigree well with autosomal dominant so we are now full proof to say this is an autosomal dominant trait this is the second pedigree that we are looking out let us look at it first thing that we want to look whether it is an autosomal or x-linked how do you find it out whether the distribution pattern see one two three four males affected one two three four females are affected so 50-50 distribution is no way it is going to be an x-linked so it is obviously another autosomal trait now let us look another thing here if you see very carefully you will find neither mother nor father are affected none of them are affected but one of their child is affected what does that mean mother father parents don't have the disease children have the disease the only way it's possible if the disease is following autosomal recessive trait isn't it I told you about this rule earlier these rules are golden for guessing this whole pedigree very very fast you do not need to actually calculate through all of that to get there I show you one example how much time it consumes to calculate this whole thing so this type of rules will actually help you to get to the depth so it is autosomal recessive pedigree let us move to the third kind in this pedigree we see one two three four five five males affected three females affected now by looking at this we can tell it could be either autosomal or sex linked the chances for sex linked are rare because it is kind of distributed between both male and female but let us look at it in further details you see here the disease is transferred from mother to son and here both of them mother and father are affected and all the children are affected so if mother and father both affected and affecting all their children that means it is a form of dominant pedigree is a dominant trait and you also seen this this is in every generation mostly but if you look at here mother and father are not affected by but one of the child is affected again this means it is a kind of recessive so this pedigree is kind of puzzling and it's hard to explain with all our rules it could be either autosomal or sex linked it could be dominant or recessive how could you answer that now this type of puzzle in pedigree can be there in your exams how to solve them now let's let's take some more rules into the play into the action see here the disease is transferred from the father to son father is affected son are also affected and I told you earlier it is a golden rule that if x-linked recessive disease is there it should never transfer from father to son so it is definitely not x-linked recessive now as we see mother to son transfer is going on here also mother to son transfer is going on so and here also you see a son is affected there is a chance that one of the mother can be a carrier of the disease who is transferring it carrier means if it is a recessive form of the disease the carrier can transfer the disease to the next generation right so this type of pedigree is you can't really explain well with either of our ideas so based on that what we can find it is not x-linked because it is not excelling dominant it is not x-linked recessive now if it is excelling it is autosomal dominant or autosomal recessive let us take that one in the case so it is definitely not excellent we know that it is autosomal among autosomal either it could be dominant or it would be recessive now if it is a dominant then obviously this thing will not result right if it is a dominant trait then to parent none of them getting the disease will not get a deceased offspring right it is only possible in case of recessive disease right and in recessive disease though two parents are affected all the individuals all the offsprings are affected this is rare but we can get this disease so the only way to explain this pedigree is autosomal recessive trait so take this one in this account autosomal recessive now in this type of pedigree where you have confusion you need to test your theory there if it is an autosomal recessive trait then how can you explain you take here so the disease will show up let us say the disease gene is small a so the disease will show up if small is small a is present that is in recessive format now this is again capital a small a or capital a capital we do not know but we in either way it's not showing any disease in the next generations we have this affected we have this one affected so definitely as so sorry affect unaffected I'm sorry affected and affected writer so as this two individuals are affected that means obviously the father all should have a small a coming in so we know the sure that the phenotype the genotype for the father will be capital is small a right so now if its capital is small in this mother could be capital is small in this one also could be capital is smaller for example now capitalist mala means it is a carrier so it is not getting the disease but it carries the small aging and transfer it to the next generation and cause it to show the disease it is marrying another healthy man over here and that is capital a capital a or capital is small a now if they marry together one of their child is getting the disease so small as small a should be the film genotype so to become the genotype small as small a the new person who this woman will marry should have a small a so we know for sure the genotype for this person will be capital a small a and then we can explain rest of them very clearly so yes with the help of autosomal recessive pedigree autosomal recessive inheritance we can actually explain this whole pedigree that is how we can go so for this complicated one you can go for this approach of finally checking them now the fourth one the fourth type of pedigree let us see that this is the last one we want to solve so here you see males are affected in s females are affected more okay and again in this case kind of distributed between male and female and here you see one important thing that the disease is transferred to the daughter from the father this is a very important golden rule the disease is transferred from father to daughter so if one father is affected all the daughters will be affected remember what kind of pedigree we are talking about x-linked dominant in case of x-linked dominant whenever you see this idea that father is affected and all the daughters are affected it means x-linked dominant without anything you can put x-linked dominant and that is correct okay and in x-linked dominant the distribution is kind of pine between male and female okay and you see this is more transferred here from mother to son less but from father to daughter all the daughters are getting the disease so we can easily write that down as x-linked dominant over here this is how you should solve all the pedigree questions okay I hope this video helped you to understand how to solve pedigree questions both using the rules as well as using the traditional methods so thank you for watching please subscribe to my channel to get more videos like that and share this video with your friends thank you

Channel: Shomu's Biology

Views: 656,124

Keywords: suman bhattacharjee, shomus biology, pedigree analysis, pedigree, pedigree analysis problems, pedigree analysis by suman bhattacharjee, how to analyze pedigree, dominant pedigree, recessive pedigree, x linked pedigree, genetics, family tree analysis

Id: 9IsUSaQqk5M

Length: 22min 13sec (1333 seconds)

Published: Mon May 16 2016