x-linked diseases

[marsalien]

Both haemophilia and colour blindness are se-linked recessive but chances for haemophilia to occur are less as compared to that for colour-blindness.why?

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[coffeebythelake]

I don't think it is a matter of genetic penetrance or expressivity, simply the fact that more people in the population carry the allele for color blindness. This might be because hemophilia is a potentially life threatening medical condition, whereas color blindness is usually only an inconvenience.

 

[wannabedocta]

Both haemophilia and colour blindness are se-linked recessive but chances for haemophilia to occur are less as compared to that for colour-blindness.why?

I don't understand the significance of this question. These two different sex linked recessive diseases are independent of each other, are they not? as are a whole host of other sex-linked recessive diseases. They all aren't expected to have to same occurence. Different diseases are attributed to different genes arranged differently on chromosomes so they will not have the same occurence.

 

[Kaustikos]

They all aren't expected to have to same occurence. Different diseases are attributed to different genes arranged differently on chromosomes so they will not have the same occurence.

Not according to darwin

 

[fileserver]

Great answer, e.

Edit: Nvm.. didn't notice you are a med student on my mobile phone.

 

[marsalien]

I think eikenhein iz right....my teacher also told me the same thing(he iz also a dr.)

 

[marsalien]

finish what??

 

[marsalien]

finish what??

@ ekienhein

 

[DrMattOglesby]

lets say a man has a dominant sex-linked disease on the X chromosome.
he mates with a female with no gene of said disease.

the probability of any of their children having the disease are 50% ...right?
and the probability of a boy having the disease is 0%
the probability of a girl having the disease having the disease is 100%

does that follow the rules of mendel?

 

[wannabedocta]

Yea, that's what i got using the punnet square.

 

[DrMattOglesby]

lol...i guess making a punnet square could simplify things.
im just trying to get to the point where i can "think about it" and then magically come up with the answer...kinda like using nifty shortcuts in math i guess.

okay here is another one:

a man has a sex linked disease.
a female also has it.
what (if anything) can you imply about its dominance/recessiveness?
which chromosome is it on?
if they mated and had offspring, what percentage of boys would inherit the disease? what percentage of girls would inherit the disease?

 

[coffeebythelake]

lol...i guess making a punnet square could simplify things.
im just trying to get to the point where i can "think about it" and then magically come up with the answer...kinda like using nifty shortcuts in math i guess.

okay here is another one:

a man has a sex linked disease.
a female also has it.
what (if anything) can you imply about its dominance/recessiveness?
which chromosome is it on?
if they mated and had offspring, what percentage of boys would inherit the disease? what percentage of girls would inherit the disease?

Little tricks aren't necessary. It isn't hard. Work it out.

Just remember that fathers give X chromosome only to their daughters, and mothers give X chromosome to both sons and daughters.

 

[wannabedocta]

lol...i guess making a punnet square could simplify things.
im just trying to get to the point where i can "think about it" and then magically come up with the answer...kinda like using nifty shortcuts in math i guess.

okay here is another one:

a man has a sex linked disease.
a female also has it.
what (if anything) can you imply about its dominance/recessiveness?
which chromosome is it on?
if they mated and had offspring, what percentage of boys would inherit the disease? what percentage of girls would inherit the disease?

The female could be a carrier for a dominant disease and express it or she could be homozygous recessive and express it if the disease was recessive. Without knowing her genotype, I don't think you could determine % risk of offspring getting the disease. I think the only way to know for sure is if you had an actual pedigree.

 

[coffeebythelake]

The female could be a carrier for a dominant disease and express it or she could be homozygous recessive and express it if the disease was recessive. Without knowing her genotype, I don't think you could determine % risk of offspring getting the disease. I think the only way to know for sure is if you had an actual pedigree.

1. You can't be a carrier for a dominant disease, only a recessive one.
2. It is possible to determine risk to potential offspring. In the practice of medicine, it is called genetic counseling.

 

[wannabedocta]

Heterozygous Dominant then?

 

[DrMattOglesby]

i dont think there is sufficient information to solve that problem.
anyways, is there such a thing as a Y-linked disease?
if so...how come we dont study them in genetics for the MCAT?

 

[wannabedocta]

I think it's because the Y chromosome is really small and mostly devoted to genes involved in male sex characteristics.

 

[Kaustikos]

anyways, is there such a thing as a Y-linked disease?

Yes, it causes a large protrusion from the scrotum.

 

[Foghorn]

lol...i guess making a punnet square could simplify things.
im just trying to get to the point where i can "think about it" and then magically come up with the answer...kinda like using nifty shortcuts in math i guess.

okay here is another one:

a man has a sex linked disease.
a female also has it.
what (if anything) can you imply about its dominance/recessiveness?
which chromosome is it on?
if they mated and had offspring, what percentage of boys would inherit the disease? what percentage of girls would inherit the disease?

This might help you.
http://forums.studentdoctor.net/showpost.php?p=5216436&postcount=2

 

[coffeebythelake]

Yes, it causes a large protrusion from the scrotum.

Actually that's quite close. The SRY (sex determining gene of Y) is associated with a number of genetic defects like androgen insensitivity syndrome.

 

[Caesar]

lets say a man has a dominant sex-linked disease on the X chromosome.
he mates with a female with no gene of said disease.

the probability of any of their children having the disease are 50% ...right?
and the probability of a boy having the disease is 0%
the probability of a girl having the disease having the disease is 100%

does that follow the rules of mendel?

Be careful. Everyone has the same gene, its Alleles that are dominate or recessive, My Genetics prof asked tricky questions like that. So its more correct to day he has the dominate allele and she has recessive.

 

[coffeebythelake]

Be careful. Everyone has the same gene, its Alleles that are dominate or recessive, My Genetics prof asked tricky questions like that. So its more correct to day he has the dominate allele and she has recessive.

Nice catch, didn't even notice that.

 

[Caesar]

Nice catch, didn't even notice that.

Sweet can I get into your med school for free now? please?