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* @sarim
 #692422  
  mle2014 - 08/09/12 20:43
 
  can you pls help us on the angioedema concept
how c1q levels vary in hereditory vs acquired?
 
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* Re:@sarim
#2713357
  mle2014 - 08/09/12 20:45
 
  http://www.usmleforum.com/files/forum/2012/1/692326.php is the ref.Qn  
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* Re:@sarim
#2713449
  mle2014 - 08/09/12 23:12
 
  sarim have you done nbme12 i've some doubts in genetics section..can you help me ?  
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* Re:@sarim
#2713486
  sarim - 08/10/12 00:12
 
  i haven't taken it yet but please go ahead with the Q.  
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* Re:@sarim
#2713717
  mle2014 - 08/10/12 06:04
 
  Q1.whats the difference b/w unfavourable lyonization and non disjunction?
vignette=>hemizygous muscular dystrophy

Q2.pedigree chart block2 qn44
i dont understand significance of a LINE sequence

 
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* Re:@sarim
#2713923
  sarim - 08/10/12 15:20
 
  Q1-30 yo woman whose child has DMD comes bec of progressive weakness during the past 3 years. A muscle biopsy specimen obtained from the woman shows findings typical of hemizygous muscular dystrophy. Which of the following is the most likely explanation for these findings?

a.) chromosomal translocation
b.) maternal chromosome constitution 45,X
c.) nondisjunction
d.) unfavorable lyonization

"D" is correct

-no need for comparing "D" with "C" , as it is not in reference to Trisomies or monosomies.


"Unfavorable LYONIZATION" :

-aka "Unfavorable X-inactivation" or "Unfavorable Skewed X-inactivation"

-DMD is an X-linked recessive

-In FEMALE, each somatic cell under goes "Random inactivation of X-chromosome"(to form a barr body) and that create "Somatic Mosaicism" of two X-chromosomes that she inherited.

-If this X-inactivation is Skewed,

say like if a female who is carrying one bad and one good copy of X-chromosomes and if more than 80% of the good copy X-chromosome get inactivated ------then what's left is the majority of the "Bad Copy X-chromosomes"-----this will manifest the x-linked recessive disease in that female----- that is why said to be "UNFAVORABLE"

as is the case in the stem


Q2-In this case u don't even need to look at the pedigree.

Neurofibromatosis Type-I:

-Autosomal Dominant
-Highly Variable Expression
-Complete Penetrance
-50% cz of New Mutations


Line sequence ? i didn't get ur Q.
 
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* Re:@sarim
#2714000
  sarim - 08/10/12 17:34
 
  Regarding Q1 :

Going over the Q , just noticed that it's referring to "HEMIzygous" status .

In that case "B" should be the right answer. (Maternal chromosome constitution 45,X)


-In rare cases All the given options can manifest a X-linked recessive in a Female BUT only Option "B" will represent "HEMIzygous" status




A-Chromosomal Translocation:

-probably referring to "X-autosomal Translocation" as the cause of manifestation of X-linked recessive d/o in FEMALE


C-Non-disjunction:

-probably referring to the Meiosis-II Non-disjunction of X-chromosome leading to
"Uniparental Isodisomy" as the cause of manifestation of X-linked recessive d/o in FEMALE





D-"Unfavorable LYONIZATION" :

-aka "Unfavorable X-inactivation" or "Unfavorable Skewed X-inactivation"

-DMD is an X-linked recessive

-In FEMALE, each somatic cell under goes "Random inactivation of X-chromosome"(to form a barr body) and that create "Somatic Mosaicism" of two X-chromosomes that she inherited.

-If this X-inactivation is Skewed,

say like if a female who is carrying one bad and one good copy of X-chromosomes and if more than 80% of the good copy X-chromosome get inactivated ------then what's left is the majority of the "Bad Copy X-chromosomes"-----this will manifest the x-linked recessive disease in that female----- that is why said to be "UNFAVORABLE"


Thanks.
 
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* Re:@sarim
#2714039
  mle2014 - 08/10/12 18:45
 
  hi sarim I was mentioning this one for Q2,tnx a lot for the explanations it really helped.

Q2. An investigator is studying a large family with many members who are affected by a disorder caused by a fully penetrant autosomal dominant inherited gene mutation. A pedigree is shown. Most affected members also have a rare allele at a locus thought to be closely linked to the disease locus. A father (individual III-3) and his daughter (individual IV-3) have the disorder, but they have the wild-type allele at the linked locus. Which of the following is the most likely cause of these findings?

A. Insertion of a LINE sequence
B. Random segregation
C. Recombination
D. Single nucleotide polymorphism
E. Transduction
 
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* Re:@sarim
#2714309
  sarim - 08/11/12 04:15
 
  my pleasure :)

what's ur pick on this one ?
 
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* Re:@sarim
#2714331
  step1.sam - 08/11/12 06:38
 
  PLEASE PLEASE SEND ME QUESTION FILE OF NBME 13, I DO HAVE THE ANSWERS JUST NEED THE QUESTIONS....SO SHORT OF TIME...THANKS...MY SKYPE ID IS CAPRICORN2224...YOU MAY POST IT HERE AS WELL

GOD BLESS
 
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* Re:@sarim
#2714336
  mle2014 - 08/11/12 08:14
 
  m confused between option AA and DD, for the test I chose DD as I had never heard of line seq!!!
later as I read on the topic found the stuff still confusing. can these Line sequence insert a single nucleotide?
 
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