Prep for USMLEPrep for USMLE
         Forum      |     Resources New Posts   |   Register   |   Login





 hemophilia  




Post Reply  
  • 0/5
  • 1
  • 2
  • 3
  • 4
  • 5


Author30 Posts
  #1

women is pregnant, father has hemophilia, what is the chance that baby will have hemophilia
1. 25%
2. 50%
3. depends on gender
4. as in population




  #2

should be 25%.
since there is an equal chance that mom might be homozygous XX or carrier xX.
so out of the 8 probabilities, 2 offspring can have hemophilia... one boy and one girl (who gets the defective gene from both father and mother).

correct me if im wrong, tho.


  #3

3 ...


  #4

i also go with 3


  #5

arpita1586 wrote:
should be 25%.
since there is an equal chance that mom might be homozygous XX or carrier xX.
so out of the 8 probabilities, 2 offspring can have hemophilia... one boy and one girl (who gets the defective gene from both father and mother).

correct me if im wrong, tho.


women is pregnant, father of the fetus has hemophilia, chance for the baby to have hemophilia is ???, count again, do not overshoot smiling face



  #6

3


  #7

plz correct me if i am wrong
if father has haemophilia
so all his daughters will be carriers and all his sons are normal

so none will have the disease
unless the rare manifesting female heterozygos

so we can say none will have haemophillia
or 4. as in population


  #8

good point Madoo but we don't know, if the mother is a carrier confused

your explanation is correct, if the mother isn't a carrier.

"If a male is afflicted with the disease and has children with a female who is not even a carrier, his daughters will be carriers of hemophilia. His sons, however, will not be affected with the disease. The disease is X-linked and the father cannot pass hemophilia through the Y chromosome. Males with the disorder are then no more likely to pass on the gene to their children than carrier females, though all daughters they sire will be carriers and all sons they father will not have hemophilia (unless the mother is a carrier)." (http://en.wikipedia.org/wiki/Hemophilia)

But if she is a carrier all daughters will be carriers, but 50% of her sons can have hemophilia, am I right?


  #9

Callie wrote:

But if she is a carrier all daughters will be carriers, but 50% of her sons can have hemophilia, am I right?


in x linked if mother is a carrier so:- 50%of her daughters are carriers and 50%of her sons have the disease
"unless u mean that a carrier mother marry a diseased father which is another story and a very rare condition which is not the issue in this question"


n.b in this question the diseased man is the father of the fetus and not the pregnant lady
right ?? raised eyebrow



Edited by madoo on Jun 28, 2009 - 10:35 AM

  #10

Yes, I meant a marriage between a carrier mother and a diseased father smiling face



  #11

so u r right
but in this question mother is homozygos normal and father has the disease

so 100% of their daughter are carriers and none of their sons have the disease

so the answer is 4. as in population

and answer no: 3 wolud be right if the question was asking what is the chance that baby will have the mutant allel


  #12

madoo wrote:
plz correct me if i am wrong
if father has haemophilia
so all his daughters will be carriers and all his sons are normal

so none will have the disease
unless the rare manifesting female heterozygos

so we can say none will have haemophillia
or 4. as in population


yep, that's correct, they don't give mother's family history, so, assume she is not a carrier, so, risk as in population to have a disease in this fetus




  #13

madoo wrote:

...n.b in this question the diseased man is the father of the fetus and not the pregnant lady right ?? raised eyebrow

yes


  #14

good discussion.


  #15

Yes, I meant a marriage between a carrier mother and a diseased father .


but if mother is carrier and father is affected -------------

so xX and father is xY

then their children will have xx , xY ,Xx ,XY

then one affected female child xx
one is affected male child
one is female carrier
one normal male child

if mother is normal homozygous
then:
50% daughters are carriers and sons normal


if i am wrong pls correct me




  #16

dr_radha wrote:

if mother is normal homozygous
then:
50% daughters are carriers and sons normal


if i am wrong pls correct me


if mother is normal homozygous
and father is affected
100% of daughters and all sons are normal

remmeber father will give his diseased x to all his daughters


  #17

sorry madoo , tht by mistake i typed smiling face.

thanx for bringing it up

ya it is 100% daughters are carrirers

wht about wht calliie wrote abt the other scenario i-e mother carrier and father affected
is my conclusion rite?




  #18

wink i have never read it in any source
but seems logicnod


  #19

So just in case I will get a similar question, where nothing is said about the mother's history I should assume, that the mother is totally healthy smiling face yes?

So the final answer will be, like Madoo said, 4? smiling face

Tricky question (although it seemed trivial at first sight )- thanks for the great discussion nod


  #20

Unclear question about mom history
If mom is healthy , so no child will have the disease , so go for 4
If mom is a carrier , there are 50% of her children will have the disease (25% boys and 25% girls ), 25% girls will be carriers, 25% boys will be normal . So the answer will be 2 .
Do we should assume mom is healthy ?





Bookmark and Share





Login or Register to post messages








show Similar forum topics

hemophilia
hemophilia a and b
Hemophilia
show Related resources









Advertise | Support | Privacy | TOS | Premium | Contact