welcome science friends to sex linkage punet squares we're going to use Queen Victoria and her family as an example for making our sex linkage punet squares Queen Victoria's family is famous for having hemophilia this is a sex linked trait that is passed down throughout generations and way back when with a lot of royalty they liked to keep royalty in the family so they married a lot of their own family cousins very close relatives now Queen Victoria was something called a carrier when we're talk
ing about sex linkage inheritance carriers are females and they're females because of that ex chromosome redundancy there are females who carry recessive genes but because of the redundancy of the X chromosome they often carry that Gene but it is not expressed so they carry that recessive trait even if they do not express it but because it's on an X chromosome the sex chromosome it is passed on to their offspring and their children well that means if those children are males there's a higher lik
elihood that they will Express that recessive gene because they don't have that redundancy of 2x chromosomes so let's look at hemophilia we're using x's and Y's for our large letters and for hemophilia we're going to use the letter H hemophilia is a recessive sexlink trait so we must have a little H little H if it's a female or just little h with a Y chromosome for males because they only have the one X chromosome to set up a sexlink ponent square we need to first break down what the gametes are
going to be to be on the outside of our punet Square so here we have the circle to represent the female and a square to represent the male a female is going to donate One X chromosome to each of her gametes so we're going to have an X and an X for our two gamet on the outside of our punet Square attached to those X's are the letters for the genotype of Hemophilia we have a big h on one and if we're looking at a carrier they're carrying the recessive trait on the other X chromosome so we have a
little H for the other X chromosome and we're going to put them on the out side of our pet Square it doesn't matter if it's the top or side I just decided to put the female on the side the male is going to donate an X chromosome this male does not have hemophilia he has a capital Big H and has a y chromosome and since this Gene is only found on the X chromosome there's nothing that goes on the Y the Y is just there it's just by itself it does not carry this Gene so we don't put an H on the WT we
're going to put the X with a big H and the Y on the top of our punet Square doesn't matter if it's the top or side I just decided to put it on the top now we just fill out our punet square like normal our first Offspring will have 2 x is one from Mom one from Dad and both of those H's are big H's one big H from Mom one big H from Dad the next Offspring to the right it will be male it has One X from Mom and one y from Dad and the H attached to the x is a large H so they will not be hemophilic th
e third child again will be female an X from Mom and an X from Dad Big H from Dad a small H from Mom means that this female child will be a Carri she does not have hemophilia but she carries that recessive gene for hemophilia she could possibly pass it down to her children our last child is a male an X from Mom and a y from Dad and they have the little H from Mom and because it's just the little H there's no redundancy the little h means that this male child will have hemophilia this is why male
s often have those Sex Link traits expressed because whatever they get is what they express Express so when we're looking at these different alals women or biological females have three different types of genotypes they have what's called normal which is homozygous dominant they have the carrier status which is heterozygous females can also be homozygous recessive for exlink traits in this example we're using color blindness as a sexlink recessive trait so a normal woman in this circumstance wou
ld not be color blind the carrier would not be color blind because they still have that Big B to help protect them but the homozygous recessive individual will be color blind because they have both recessive alal in their genotype for men or males there's only two possible genotypes they could be normal with the dominant not color blind in this example or they could be color blind whatever the male gets on his ex chromosome is what will be expressed so female again have that protection of the re
dundancy of two X chromosomes the male does not get that advantage that was Sex Link punet squares I hope it helped
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