GoodGirl
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A 4-year-old boy presents to the physician’s office with coarse facies,
short stature, stiffening of the joints, and mental retardation. Both parents,
a 10-year-old sister, and an 8-year-old brother all appear unaffected. The
patient’s mother is pregnant. She had a brother who died at 15 years of age
with similar findings that seemed to worsen with age. She also has a
nephew (her sister’s son) who exhibits similar features. Based on the probable
mode of inheritance, the risk that her fetus is affected is
a. 100%
b. 67%
c. 50%
d. 25%
e. Virtually 0
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| nerve09
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d.25%
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| new_n_lost
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No i hate them so much that i cant describe. they make me cringe.
Seems to me like a Xlinked recessive so i would say 25%
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| GoodGirl
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NNL, I know what you talking about, same feeling here.
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| GoodGirl
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Both of you got it right.
d,
The fact that the mother of the affected child
has an affected brother and an affected nephew through her sister suggests
X-linked recessive inheritance. This is made more likely because the
symptoms suggest a mucopolysaccharidosis (storage of glycosaminoglycans)
and because one type exhibits X-linked recessive inheritance
[Hunter’s syndrome or MPS type II (309900)]. When evaluating the possibility
of an X-linked disorder, it is important to remember the pattern of
inheritance of the X chromosome. Females have two X chromosomes,
which are passed along in a random fashion. They pass any given X chro-
mosome to 50% of their sons and 50% of their daughters. For an X-linked
recessive condition, those daughters who inherit the affected allele are
heterozygous carriers of the disorder but are not affected. Since males
have only one X chromosome, those who inherit the affected allele are
affected with the disorder. Given X-linked recessive inheritance, the
mother must have the abnormal allele on one of her X chromosomes (she
is an obligate carrier) in order for her son and brother to be affected. The
fetus thus has a 1/2 chance of being a boy and a 1/2 chance of being affected
given male sex, resulting in a 1/4 (25%) overall risk of being affected.
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| lakshya_0_7
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very good q goodgirl...
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| nerve09
Forum Junior
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hmm thank u good girl ..i read too much genetics
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| ShweHope99.9998
Forum Fanatic
Topics: 12
Posts: 2,436
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I thought I love the genetics, but this is more in my eye as stat that am not sure love it or not
Any way , thnx GG , keep more coming .
GL
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