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anyone?
Can't see the question because it requires a login username and password which I'm assuming only you can access. Sorry, can't help there...
maybe get a screenshot of the question?
Original post by noheartattack
Can't see the question because it requires a login username and password which I'm assuming only you can access. Sorry, can't help there...
maybe get a screenshot of the question?


Oh sorry about that, here it is:
question.jpg
All which are not homozygous, maybe ?
Original post by DavidYorkshireFTW
All which are not homozygous, maybe ?


How would you know which ones are homozygous?
Original post by tammie123
How would you know which ones are homozygous?

Because they would have haemophillia
Original post by DavidYorkshireFTW
Because they would have haemophillia


But haemophilia is only on the X chromosome so not everyone with haemophilia will have be homozygous :confused:
Reply 8
Original post by tammie123
Oh sorry about that, here it is:
question.jpg


Any female that produces a haemophiliac son must be heterozygous (ask me if you don't understand why this is). For the females that have not reproduced, it's not possible to say whether they are heterozygous or not. Even for II-1, it's not possible to say whether she is heterozygous or not because she would only produce haemophilac sons with a probability of 50% (ask me if you don't know why this is).

Yeah, so I'm unless I'm missing a trick, the question is badly worded, because one can only say definitively that a female is heterozygous but not that she is not heterozygous. Also, the question is badly worded in another sense that one cannot technically be heterozygous for haemophilia, but only for the actual allele that causes it (i.e. people are heterozygous for alleles, not traits).
(edited 10 years ago)
Original post by Ashnard
Any female that produces a haemophiliac son must be heterozygous (ask me if you don't understand why this is). For the females that have not reproduced, it's not possible to say whether they are heterozygous or not. Even for II-1, it's not possible to say whether she is heterozygous or not because she would only produce haemophilac sons with a probability of 50% (ask me if you don't know why this is).

Yeah, so I'm unless I'm missing a trick, the question is badly worded, because one can only say definitively that a female is heterozygous but not that she is not heterozygous. Also, the question is badly worded in another sense that one cannot technically be heterozygous for haemophilia, but only for the actual allele that causes it (i.e. people are heterozygous for alleles, not traits).


Yeah this is confusing me too :frown:
Reply 10
Original post by tammie123
Yeah this is confusing me too :frown:


As far as I'm aware, your teacher just wants you to identify the mothers producing haemophiliac sons, but they haven't worded the question properly. There's no way that you could possibly determine whether a woman is heterozygous or not in the pedigree if she hasn't reproduced. So that's it really, you should be able to move onto the next question.
Original post by Ashnard
Any female that produces a haemophiliac son must be heterozygous (ask me if you don't understand why this is). For the females that have not reproduced, it's not possible to say whether they are heterozygous or not. Even for II-1, it's not possible to say whether she is heterozygous or not because she would only produce haemophilac sons with a probability of 50% (ask me if you don't know why this is).

Yeah, so I'm unless I'm missing a trick, the question is badly worded, because one can only say definitively that a female is heterozygous but not that she is not heterozygous. Also, the question is badly worded in another sense that one cannot technically be heterozygous for haemophilia, but only for the actual allele that causes it (i.e. people are heterozygous for alleles, not traits).


to be heterozygous either their father must have haemophilia or the mother must be a carrier, that's all I've worked out so far
Reply 12
Original post by tammie123
to be heterozygous either their father must have haemophilia or the mother must be a carrier, that's all I've worked out so far


Okay, let's do it this way:

1)The only haemophiliacs in the pedigree are male.

2)Males are XY. Therefore, they must have gotten a mutant allele from their mother.

3)No females in the pedigree are haemophiliacs. Therefore, every female that produces a hameophiliac son must be heterozygous for the mutant allele.

See?

If you look at the pedigree, you should find that every female that has had children in the pedigree has produced haemophiliacs, and therefore must be heterozygous. The only exception if II-1; so for II-1 it's not possible to say whether she is heterozygous or not.
Reply 13
Haemophilia is an X link recessive disease.

These conditions only affect men. It is extremely rare to see a women affected (they would need to have fathers who had the condition and mothers who were carriers and even then it would only be a 50% chance of being affected).


Man unaffected X Y

Man affected XY


Female carrier X X ("heterozygous")

Female unaffected X X ("homozygous")

In the question female carrier is called "heterozygous" since they have one normal and one abnormal X.


All X-linked recessive conditions follow a common inheritance pattern.

Normal male X Y + Carrier Female X X

Offspring:

1/4 - Normal male X Y
1/4 - Normal female X X
1/4 - Female carrier X X
1/4 - Haemophilia male X Y

This is the royal family showing haemophilic men and female carriers.

As you can see all the children affected have mothers who are carriers and you see this will all recessive X linked conditions.

http://3.bp.blogspot.com/-5G8wDgFU9Ec/TvvGIUNEuHI/AAAAAAAAEhc/inykTqHQ9_k/s1600/ftree.gif

HTH
(edited 10 years ago)
Reply 14


Again, that image is problematic because they wouldn't be able to say whether Helena and Louise where carriers or not without genotyping (technology wasn't available in those days). One cannot also say with certainty that Victoria (who married Frederick) wasn't a carrier.
Original post by Ashnard
Okay, let's do it this way:

1)The only haemophiliacs in the pedigree are male.

2)Males are XY. Therefore, they must have gotten a mutant allele from their mother.

3)No females in the pedigree are haemophiliacs. Therefore, every female that produces a hameophiliac son must be heterozygous for the mutant allele.

See?

If you look at the pedigree, you should find that every female that has had children in the pedigree has produced haemophiliacs, and therefore must be heterozygous. The only exception if II-1; so for II-1 it's not possible to say whether she is heterozygous or not.


Original post by Revenged
Haemophilia is an X link recessive disease.

These conditions only affect men. It is extremely rare to see a women affected (they would need to have fathers who had the condition and mothers who were carriers and even then it would only be a 50% chance of being affected).


Man unaffected X Y

Man affected XY


Female carrier X X ("heterozygous")

Female unaffected X X ("homozygous")

In the question female carrier is called "heterozygous" since they have one normal and one abnormal X.


All X-linked recessive conditions follow a common inheritance pattern.

Normal male X Y + Carrier Female X X

Offspring:

1/4 - Normal male X Y
1/4 - Normal female X X
1/4 - Female carrier X X
1/4 - Haemophilia male X Y

This is the royal family showing haemophilic men and female carriers.

As you can see all the children affected have mothers who are carriers and you see this will all recessive X linked conditions.

http://3.bp.blogspot.com/-5G8wDgFU9Ec/TvvGIUNEuHI/AAAAAAAAEhc/inykTqHQ9_k/s1600/ftree.gif

HTH



Thank you so much! This was really helpful :smile:
(edited 10 years ago)
Original post by Ashnard
Again, that image is problematic because they wouldn't be able to say whether Helena and Louise where carriers or not without genotyping (technology wasn't available in those days). One cannot also say with certainty that Victoria (who married Frederick) wasn't a carrier.


For question 3, I basically drew a punnet square and said that the females have a 1 in 2 chance of being heterozygous, is there more I can say about this or is that enough?
punnet square.jpg
Reply 17
Original post by tammie123
For question 3, I basically drew a punnet square and said that the females have a 1 in 2 chance of being heterozygous, is there more I can say about this or is that enough?
punnet square.jpg


Yeah, 50% is right. That should almost definitely be enough, as you've given the answer and shown how you got to it. There's nothing else to add, really..

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