NBME 6 block 3 q1 to 50 - maryam2009

[ArchivalUser]

hey maryam i also chose D for question 10 but it was a total guess.. can u please explain y you picked it ????

[ArchivalUser]

and also the answer for 13... hate that question... can you please explain...

[ArchivalUser]

15 CCC...

16 BBB

17 BBBB

[ArchivalUser]

14.EE

Many intraerythrocytic hemoparasites survive the host immune system through rapid antigenic variation. Among babesial parasites antigenic variation has been demonstrated convincingly only for Babesia bovis and Babesia rodhaini. The molecular basis for antigenic variation in babesial parasites and its possible connection with cytoadherence and sequestration are discussed.

posted by doc_study

[ArchivalUser]

****************************10-CCC************************************
posted by sarim

"STREAKING": is is a technique used to inoculate organism on agar plate.For this we use cotton swab or "Inoculant WIRE Loop" which is a wire that have very small loop at it's tip.

http://upload.wikimedia.org/wikipedia/co...n_loop.JPG

At first we sterilize and then dip this loop into sample that we have collected.Now we roll it on 1/4th of the agar plate(Just like u see in stem pic the region marked with "A").

Second Next we sterilize the loop again and this time we don't dip it in the collected sample rather we drag it over the FIRST 1/4th inoculated region which will pick up the organisms and spread it to the next 1/4th space on the agar plate.

Third Next we sterilize the loop again and this time we drag it over the SECOND 1/4th inoculated region which will pick up organisms and spread it to the next 1/4th space on the agar plate.

Fourth Next we reapeat the same previous step to spread on the last 1/4th space on the agar.

** Every time we repeat the streaking it picks up fewer and fewer organisms and in the end we end-up separating the "PURE COLONY OF SINGLE ORGANISM" as u see the colony that is marked with "D".Now in our second step of streaking we got Gray and White colonies but not the black one and again in the third step we just got Gray colonies which means the black one was not present at all in 2nd and 3rd 1/4th region of agar but showed up on the fourth step that tell us that it was contaminated as is also present in the first 1/4th streaked space.

http://video.google.com/videoplay?docid=...8873922892#

posted by sarim

15.CC
.................NADHNAD+..............
Pyrovate.................................................Lactate
.................pyrovate dehydrogenase.............

16.BB

Malaria
The disease results from the multiplication of malaria parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases progressing to coma, and death.

humans malaria is caused by P. falciparum, P. malariae, P. ovale, P. vivax and P. knowlesi. P. falciparum is the most common cause of infection and is responsible for about 80% of all malaria cases, and is also responsible for about 90% of the deaths from malaria.

Relapse is specific to P. vivax and P. ovale and involves re-emergence of blood-stage parasites from latent parasites (hypnozoites) in the liver.

Malaria develops via two phases: an exoerythrocytic and an erythrocytic phase. The exoerythrocytic phase involves infection of the hepatic system, or liver, whereas the erythrocytic phase involves infection of the erythrocytes, or red blood cells.

Symptoms of malaria include fever, shivering, arthralgia , vomiting, anemia (caused by hemolysis), hemoglobinuria, retinal damage, and convulsions.
The classic symptom of malaria is cyclical occurrence of sudden coldness followed by rigor and then fever and sweating lasting four to six hours, occurring every two days in P. vivax and P. ovale infections, while every three days for P. malariae. P. falciparum can have recurrent fever every 36–48 hours or a less pronounced and almost continuous fever

Treatment:
Chloroquine
Primaquine to prevent relapse caused by p.Vivax and P.Ovale
Sulfadoxine and Pyrimethamine ,Mefloquine ,Quinine

17.BB

[ArchivalUser]

Regarding the ethics' Qs ,I just pick the answers that I think those are right, if you your opinion is different,please bring it to discuss in a separate post,then we can choose the best posted answer and add it to the block.Thank you very much.

[ArchivalUser]

18.BB

Structural glycoproteins are encoded for by HIV-1 env. gene,viral eversion of humoral immunity is more likely to occur secoundary to a mutation of the env gene.

[ArchivalUser]

19.DD

Protein kinase A (PKA) refers to a family of enzymes whose activity is dependent on the level of cyclic AMP (cAMP) in the cell, in cell biology. PKA is also known as cAMP-dependent protein kinase .

[ArchivalUser]

*******************************************************************************
***10.DD..........correction.........bcz the pointed dot is located outside the culture,so it is a lab contaminant.
*******************************************************************************

20.CC

It is a genomic imprinting......means genes are either expressed only from the allele inherited from the mother , or in other instances from the allele inherited from the father.
so in this case,,
father has......... aa.....bd.....
mother has........ bc ....bf......

2 affected kids have received their..... bd...... from their father and....bf ....from their mother
both kids have identical bd that come from their father, so it means these 2 allels are expressed as a disease ,and the healthy child who received her... aa from father ,...bf from mother. shows no sign of disease.......means the inherited allels are expressed normal and (this kids also does not have bd.)
so genes are expressed only from the allele inherited (bd) from the father.

Genomic imprinting is an epigenetic process that involves methylation and histone modifications in order to achieve monoallelic gene expression without altering the genetic sequence. These epigenetic marks are established in the germline and are maintained throughout all somatic cells of an organism.

please clarify my answer and add your opinion.TY

Posted by Sarim:

one thing i wanted to clarify that the expression of the disease in genomic imprinting is because the specific genes are "NOT EXPRESSED" cz either got methylated or deleted.

aa, bd, bc bf are the "Markers" on DNA fragments.

those who recieved the "bd marker" , got the disease, which is coming from father side...and which means genes next to these markers either deleted or got methylated and not expressed.

[ArchivalUser]

plz continue this thread,,, m so much confused about the answer key i have & my exam is 9days away, so dont have the time to search ,,,plz plz this is a favor, plz continue