Some NBME 19 confusing points

[Wanderer HitchHiker]

Hello guys,
I know that NBME 19 had been extensively discussed here but there're a few confusing points for me wish if anyone can help me with an explaination.

1-There a question about population genetics and the stem mention that (single gene disorder frequency is 1/40,000) why i considered this value as q2 (the disease frequency) not the q (allele frequency) it's an autosomal recessive disease or does single gene disorder mean something else?

2- in asthmatic patients what's the most likely part of the respiratory tract to have limited flow due to sm contraction? I answered brochioles.

3- there's a question about graves and asks about antibodies, i used to know during CK preparation that graves also have antithyroglobulin antiboies am i wrong?

4- a question about tumor grading, the answer keys say (Size) isn't that for staging .. i answered cell appearance and arrangement.

5- Bulimia question, i think it may have dental erosins on exam not caries .. why tachycardia isn't a right choice the patient is purging and use diuretics chronically for 2 years?

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[sharkbyte]

1. 1/40,000 represents q^2, the frequency of the disease. You need to sq root that to get q to get the allele frequency. You then need to find out p (1-q = p) and then take 2pq to find the heterozygous frequency, that's going to be the probability that the woman marrying into the family is heterozygous. For the man, you know his parents are both Aa because they have a child whose affected, so if you do a Punnett Square you get AA, Aa, Aa, and aa. This means that the unaffected man has a 2/3 chance of being a heterozygote. Multiply that by the probability of his spouse being a heterozygote (the 2pq from above) and then multiply by 1/4 and you'll get 1/600 as the probability of their child having the disease.

2. Bronchiole is correct

3. In Graves, the antibodies are directed against the TSH (Thyrotropin) receptor. Anti-Thyroglobulin antibodies are seen in Hashimoto's disease.

4. You're correct, tumor grade describes the morphology/appearance of the cells. Remember that tumor stage has the TNM criteria - T = size of tumor, N = lymph node involvement, M = metastasis

5. Dental caries is correct for bulimia, it simply means tooth decay. In bulimia you'd expect to see tooth/enamel decay/erosion, enlargement of the parotid glands, and the Russell's sign (calluses on the knuckles from all the self-induced vomiting).

 

[leif.erikson]

Hey trying to avoid starting a new thread but do you/anyone remember the question referring to the mouse skin transplant? It was referencing an acute rejection and asking what cells mediate the necrosis. The correct answer was T lymphocytes but I know in FA pg 211 it talks about acute rejection having a cellular CD8 component and a humoral antibody component so I was torn between B lymphocytes and T lymphocytes.

Any help is greatly appreciated!

 

[Wanderer HitchHiker]

T lymphocyte will intiate both the cellular and humoral part of the rejection so it's the cornerstone in the pathogenesis

 

[frenchyn]

Can someone show me how to do the HLA question...the likelihood that bro HLA will match his sister? I suck at immuno

 

[Wanderer HitchHiker]

Can someone show me how to do the HLA question...the likelihood that bro HLA will match his sister? I suck at immuno

1/4 it's the same probability they will get identical chromosomes from the same parents

 

[frenchyn]

1/4 it's the same probability they will get identical chromosomes from the same parents

Is it safe for me to say it follows autosomal recessive pattern? 1/4 having exactly the same, 1/4 totally different, and 1/2 half the same?

Also do you have explanation for the one with a drug, phrenic nerve and abdominal pressure...why turbocurarine but not tetratoxin since they seem to have same mechanism?

how about the one with skeletal muscle phosphorylase and AMP? why allosteric activator? first aid said competitive activator have same Vmax but act on active site instead of allosteric...so I did not pick that one. I remember one of the pics on first aid show AMP convert to cAMP activate phosphorylase kinase...so I pick covalent modifier...it is wrong...but is this AMP same as AMP-cAMP?

That is all for now. TIA.

 

[frenchyn]

Also one of the questions has answer choice as mixed restrictive/obstruction disease...can anyone tell me what that pattern will look like? Thanks again