nirmalar

Congrats - it's a good score. What schools are you considering? -Nirmala.

Forget about polynucleotide kinase. You have to use alpha-labeling if you want to tag dNTPs used in DNA synthesis - you may have to synthesize dNTPs with the alpha phosphates labeled. I know normally the bases are radiolabeled to detect the NTPs incorporated - but if you want to detect every dNTP incorporated, then you have to tag all the 4 bases (as in sanger sequencing). -Nirmala.

You're right. So, when would you use alpha/beta end-labeling? -Nirmala.

I was reading cell bio right now and I just thought of a question. In the question, it doesn't mention what type of end-labeling was done. Which one should it be - alpha or beta or gamma phosphate (32) end-labeled? -Nirmala.

Suja, Here's my rationale (I am obsessed with this problem now). Let's say you cut with BamHI only. You get 2 different-sized fragments, each of them having a potion of gene Y. You decide to use these two fragments as two different probes. You end-label them and separate them into single-strands and run the experiment. Each of the two incubation would have two end-labeled single-stranded DNA probes(one for the top and one for the bottom strand). Let's say the top strand was the template for the RNA, then you would detect the RNA in both the incubations - both of them have the top strand and they are end-labeled. If, before incubating, but after end-labeling you digest the fragments with another enzyme, you'll have only one of the strands end-labeled for each of the fragments. P-B1----------------P1 P1----------B2 B1----------------P1 P1----------B2-P You can visualize similarly for the other half of the plasmid too. If we now run the hybridization and autoradiography now, and if we assume that the top strand is the template strand, then RNA would hybridize to unlabeled P1-----B2 in this probe-incubation and to labeled B2-------P2 in the other probe and only the second one can be visualized. So, the answer for 2nd one is correct - we don't see any band on Probe-I because the RNA hybridizes to only one of the strands in the both the probes and in Probe-I, it happens to be non-labeled. For the 4th question, as explained before, if we do not cut with the 2nd endonuclease, we'll see signal in both the Probes as the RNA would hybridize to one of the strands in both of them and they are all end-labeled. The difference between the questions is: the 4th one says RNA would hybridize to end-labeled fragments in both the preparations; the 2nd one says since within a probe mixture, RNA will hybridize to only one strand and because of the experiment methodology, only one of the strands will be end-labeled and they'll be different (top strand in one probe incubation and bottom strand in another incubation) in each of the probes which would allow us specifically see which direction and what strand is the original gene transcribed from. I was too lazy to draw a picture and upload it. But, if you still can't quite get it, I can do a diagram for you. -Nirmala.

I thought of sending PM to you and then decided to wait for a week, before PMing you. I was reluctant to bother you, as this was not do or die matter. Thanks anyhow for responding. I've turned on my PM now - you could send me one once you get the booklet. Also, did you see the recombinant question I posted on another thread? -Nirmala.

This is one of the experimental question. Four questions based on the above experiment: 1. Which of the following was most likely used to label the 5' end of the DNA fragments? a. BamHI b. PstI. c. RNase A d. Polynucleotide Kinase. e. DNA ligase. 2. Which of the following best explains the observation that only one of the two end-labeled fragments hybridized to the RNA? a. The enzyme in the labeling procedure added 32 P to only one of the strands in the DNA duplex. b. Only the DNA strand from gene Y that functions as the template for transcription will hybridize to the RNA. c. Gene Y is probably composed of only single-stranded DNA. d. mRNA for gene Yis extremely unstable in the cells from which the total RNA preparation was obtained. e. PstI functions as a phosphatase in this experiment. 3. The information provided by the hybridization experiment could be used to determine which of the following about gene Y? a. Size b. Nucleotide seq. c. Base composition. d. Direction of transcription. e. Location of its promoter. 4. Which of the following best explains why the two BamHI fragments were digested with PstI following end-labeling? a. PstI and BamHI were isoschizomers. b. There are only two PstI sites on the recombinant plasmid. c. PstI digestion removes RNA from the DNA preparation. d. The two BamHI fragments could not be separated by gel electrophoresis without PstI digestion. e. Both end-labeled DNA fragments would hybridize to the RNA preparation without PstI digestion. I will post the answers maybe after few days - should give enough time for anyone who wants to attempt the question. -Nirmala. http://tinypic.com/view/?pic=e6spwj

Hi suja, I remember you mentioned, somewhere else, that the test given in the printed(&sold) ETS guide to prepare for BCMB is different from the one that is downloaded as the free prep booklet. Is that correct? I have another version of an older test and I want to check it if that's the one that is being sold. If you have the book and if you don't mind, can we check it's same or not? -Nirmala.

Thanks guys. MWM, you're right about the shaded square. One word in antonym, I remember is DEFERENTIAL; one analogy was: DISLOCATE :: POSITION. Right now, I cannot remember any more words. Though, I distinctly remember, SCs were too painful - not obscured, but just too a**l - five clauses, double negatives... I got my first RC at 9/10th question. It was a short one (2 questions). The longer one (80 lines) as 17-20 question, followed immediately by another RC (2 questions). The longer one was about aristotlean philosophy of leisure. As an aside, when I finished my exam, but before the score screen, I did a verbal research section. All I can say about new format is, woe to the test-takers from next year. The SCs can have 3 blanks - each of which can be picked independently from a column of choices. I didn't see any antonyms / analogies. Another format of SC was where you have to pick 2 correct choices(for a single blank) from a list of 6/7 choices - both would fit in the blank. I was shown some RCs during this research section, which I happily clicked along randomly. -Nirmala.

Just back from the exam. My issue topic: Parents and communities role in school system. Argument: some business recommendation based on a survey. I did well on my argument; As for the issue, it took me some time to warm up to the topic and I did OK. Verbal: Wasn't very tough; My longest RC was only 70-75 lines. The SCs were unbelievably convoluted. I didn't see any unknown words. So, I have no clue why my score was less than 700! Quant: God, took forever. I had to rush the last 5 questions in less than 5 minutes. I had two questions identical to ones already posted: 1. n= 4^x + 4^x ...repeated 4 times; what is n^2? 2. A simple set problem: 300 people surveyed; 30% did A, y% did B, z% did both A & B, how many did neither of them? 3. SD problem: s1: -3,-2,-1,1,2,3; s2: ....; s3=...... (I cannot remember exact values; it's somewhere in the forum). Three conditions were given and which were true? I had no probability or combination problems; One problem I remember though is a figure problem: A square is divided into 4 quarters; The lower left is shaded. The upper left quarter square is divided into 4 quarters, of which the lower left is shaded and this process is repeated 2 more times. What fraction of the square is shaded? That's it for now. Thanks for all the TM members(& administrators) for a wonderful and helpful forum. -Nirmala.

Guys, I was too busy for the last few days. I am giving the exam today - I can tackle this after the exam. -Nirmala.

Hi Erin, I am still getting the error message. Did you have a chance to look into the mkdir problem? -Nirmala.

-Nirmala.

MWM, even if A & 2B are just symbols (which they are not, because even & odd can only apply to integers and the question specifically says B is an integer and thus 2B is an even integer), @A=5/2A ===> @2B = 5/2(2B) (I'm not simplifying, just treating it as a single symbol) and this isn't one of hte answer choices. My guess is whoever transcribed the question had forgotten to write the expressions properly: I can read 5/2A as 5/(2A) or (5/2)A. If I take the second expression and apply my original logic, @A = (5/2)A ====> @2B = 5B which is choice number B. -Nirmala.

-Nirmala.