The study of the molecular processes of the nucleus and cell function.

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2answers
1k views

Explanation of the terms “downstream signaling” and “upstream signaling”

In molecular biology, what's the meaning of the terms "downstream signaling" and "upstream signaling"? What's the difference between them?
0
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1answer
43 views

RNase and EtOH issue

I work with RNA and I have some RNase issues. For example I am using RNeasy mini kit and at one step I use 100% EtOH. It does not say it is RNase free or not. Does absolute EtOH inhibits or removes ...
1
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1answer
108 views

How to relate human metabolic model reactions and cancer drug targets / reactome items?

Trying to find a way to take a cancer drug (from CancerDR, for instance) and infer the metabolic reactions that are affected by it in the Human Metabolic Model. Essentially, I would like to know ...
3
votes
2answers
192 views

How do I create a probe for in situ hybridization?

I tried to make the probe several times but it failed again and again. It usually turns out that the probe after hydrolysis is very very short (maybe around 50nt). I did not check the RNA before ...
10
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1answer
24k views

Why do we add salt when precipitating DNA?

All the DNA extraction protocols I have seen involve adding salts to the extraction buffer. What is the purpose of the salts? What happens if they aren't included?
3
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4answers
119 views

Translation of mRNA?

We inserted an insulin gene from human into bacteria. Will translation of the gene (protein formation) occur in bacteria? If translation occurs then why does it occurs, give a reason for this?
0
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2answers
172 views

How to determine the actual flux in the human metabolic model of a cell line?

The problem to be solved is to determine what the flux values are for the different reactions in the human metabolic model. As far as I understand, a good way to do that would be to use gene ...
1
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1answer
80 views

Do “transcription factor binding site” and “operator” mean the same thing?

Can the terms "transcription factor binding site" and "operator" be used interchangeably in all contexts when referring to a DNA sequence, e.g. regardless of a cell type, whether or not the binding ...
2
votes
1answer
114 views

Cloning of a sheep.. Dolly?

Dolly the sheep was a clone. When she was born she was eight years old on her 1st day of birth, her mother (from which she was cloned) was also eight years old. What is a molecular reason behind this ...
8
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2answers
2k views

Why is the number of PCR cycles limited?

I've been told that the maximum number of cycles in PCR is between 20 and 30. Is this true, and what are the reasons for this limitation?
5
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1answer
61 views

What method would you use to genotype SNPs in low quality samples?

What method would you use to genotype SNPs in low quality samples? I ideally want to genotype hundreds of SNPs in hundreds of scat samples (very low amount of target DNA, potentially degraded and ...
2
votes
1answer
90 views

Should I design a primer to detect virus based on NCBI genebank?

When I searched HIV on NCBI gene bank, I found 2 results from 1997: http://www.ncbi.nlm.nih.gov/genome/?term=HIV. HIV can change every day, so I think the sequence from 1997 is not useful. Is it?
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1answer
104 views

Hardy-Weinberg applied to three alleles and stimation of allele frequencies

I have this equation: Corresponds to HW in equilibria with three alleles: $(p+q+r)^2=1$ Expanding the square results: $p^2+2pq+r^2+2pr+q^2+2qr = 1$ I need to separate homozygous and ...
2
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1answer
256 views

Elution of biotinylated RNA

I am using Neutravidin Agarose beads to isolate biotinylated RNA. The thing is, in the manual it says to use 8M Guanidine-HCl, pH 1.5 for elution biotinylated molecules. As far as I know it is a very ...
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1answer
57 views

What is the impact of prolonged electromagnetic exposure on human health?

What are the health effects of being exposed to a very strong electromagnetic field caused by two resonating superconductive coils (not static magnets) for a period of years?
1
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1answer
65 views

In vitro transcription, contamination problem

I am using a RNA which is in vitro transcripted before I started my project. It turned out it is not prepared properly and has DNA contamination. Instead of perform the in vitro transcription again, ...
1
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1answer
60 views

Dilution question about RNA

I have a basic and probably silly question. I am isolating RNA with TRIzol. I have performed the basic steps and dissolved the pellet in 50 uL water. I ve measured the concentration and it was 3313 ...
8
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2answers
2k views

why is AUG the initiation codon?

Is there any reason why AUG is the initiation codon ? Why is there a need for an initiation codon ? Can't translation start with different codons?
1
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1answer
79 views

Transcribing DNA to mRNA with introns

I have a problem in my bioinformatics class that I thought I was doing right, but someone else is getting a different answer. Here is the problem: Given the following DNA sequence, ...
4
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1answer
365 views

Effect of single nucleotide deletion or insertion on primer annealing

How is primer annealing, and, consequently, PCR amplification affected by single nucleotide deletion or insertion inside the primer ? Imagine a primer like this: GCGTCATAAAGGGGACGTG (primer) and ...
3
votes
1answer
123 views

Real-time PCR delay in Cq due to insertion SNP in primer

I am collecting evidence, even anecdotal, how does single nucleotide deletion or insertion in primer region affect the outcome of real-time PCR. I am most interested in how much there is a delay in ...
2
votes
1answer
108 views

Transition/Transversion ratio

I'm taking a bioinformatics class and at this point we are just going over basic stuff about molecular biology. Half of the class is doing reading/research on our own, so there isn't much class time ...
4
votes
5answers
531 views

What is a good miniprep protocol for the class room?

I'm trying to find a good protocol for plasmid minipreps and I'm looking at 3 preps I've found: Using phenol/chloroform extract with phenol:chloroform:isoamylalcohol, isopropanol precipitation, ...
6
votes
2answers
2k views

Very high 260/230 absorbance ratio of an RNA sample

After my most recent RNA extraction, the RNA samples had very high 260/230 absorbance ratios, (ranging from 5 to 25). I've never gotten numbers like this and I know the ratio is supposed to be ~2 in ...
11
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3answers
3k views

How long can E. coli stocks be stored at -20°C?

I'm volunteering for a biohacker lab - biocurious in Sunnyvale. The have a pretty good set of equipment - gel boxes, incubators, but they don't have a -80°C freezer yet. I'd like to set up some ...
1
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1answer
37 views

Vesicular and non vesicular transport

I have to classify them either as transported in vesicles or without vesicles. What I think - Non-vesicular 2.vesicular 3.vesicular 4.vesicular 5.non-vesicular 6.vesicular 7.vesicular ...
2
votes
1answer
93 views

DNA ligase mechanism

I am unable to understand what happens to the phosphates from ATP. What are they used for ?Charging 3' end or 5'end ?
2
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1answer
234 views

How can Southern blotting be used to establish gene copy number?

I am reading a paper on a certain marine microorganism that can eat alkanes and therefore might be useful for cleaning up oil spills, etc. This sentence struck me as odd (although I am sure that the ...
3
votes
1answer
162 views

What are centromeres *really*?

I've gathered that a centromere is a a region* where the DNA is bundles up even tighter (around protein different to Histone) and chromatids are 'joined'. However I'm still mostly in the dark ...
19
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1answer
515 views

Regulation of chromatin structure

Recently, I reviewed the different levels of chromatin structure. The primary level is nucleosomes, where DNA is bound to histones, and has structural similarity to "beads on a string." The secondary ...
10
votes
1answer
453 views

What is the functional and structural distinction between core (H2A, H2B, H3,H4) and linker(H1/H5) histones?

Many explanations of histone biochemistry isn't quite elucidating for the undergraduate student. How does histone structure (dimers, octomers) relate to their specific functions as core or linker ...
2
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1answer
132 views

Histone marks mechanism

I am slightly confused about the mechanisms that makes histone modifications associate with gene expression. That is, H3K36me3 is believed to be present in actively transcribed genes, H3K27me3 in ...
9
votes
4answers
3k views

Why we have no enzyme to digest cellulose?

As we know, cellulose is the most abundant polysaccharide in nature. Why don't we have any enzyme to digest cellulose?
0
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1answer
52 views

Identifying mutations in a yeast strain

Cells of a triple-mutant yeast strain (leu- his- trp-) were spread either on minimal medium or on minimal medium supplemented with various combinations of histidine, leucine, or tryptophan. The ...
3
votes
1answer
80 views

Transposons and the net amount of DNA

The retrotransposons and certain DNA-transposons, are "jumping" sequences which may be incorporated elsewhere in the genomic DNA of an organism, through varying mechanisms. This insertion is almost ...
1
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1answer
316 views

Shine-Dalgarno sequence and expressing proteins

Shine-Dalgarno sequence present in the prokaryotic mRNA plays a role in initiation of translation. In eukaryotes a Shine-Dalgarno like sequence is present but does not play an important role in ...
2
votes
2answers
70 views

Molecular simulations without capping n- and c-terminus of polypeptide

When running molecular simulations, what is the consequence of not capping the n- and c-terminus? I have been following gromacs tutorials and haven't come across any that deal with capping the ...
8
votes
2answers
193 views

How are antibodies designed?

Antibodies have the ability of recognising highly specific peptide sequences and bind it at their antigen-binding site. This ability is harnessed as a tool in research to purify target structures in ...
2
votes
1answer
75 views

Determining sequence of oligoribonucleotide

Oligoribonucleotide X was treated with phosphatase (for removal of 3' and 5' - terminal phosphates), then with RNAase T1, which cleaves all phosphodiester bonds located in a 3' position of ...
1
vote
1answer
55 views

Clarification of the procedures to amplify cDNA needed

The typical procedure to obtain cDNA from genomic extracted DNA is the following: RNA is extracted from desired tissue, RNA/DNA hybrid is obtained by virtue of reverse transcriptase RNA dependent DNA ...
3
votes
2answers
78 views

Why not use Cu(OH)2 as a dye for protein electrophoresis?

As I know, $Cu(OH)_2$ $+$ Protein $\rightarrow$ Purple. So why not use $Cu(OH)_2$ as dye in protein electrophoresis?
4
votes
1answer
307 views

How much does the Hayflick limit/telomere length vary across taxa and within humans?

Since they seem to be quite connected, I'm curious if anyone knows of research comparing the Hayflick limit (and presumably by extension telomere length) between different taxa. I've heard the ...
2
votes
2answers
75 views

How does promoter sequence affect initiation?

I don't know if this might have been highlighted in recent research, but a textbook I have states that "the exact way in which promoter sequence affects [transcription] initiation is unclear" I'm ...
1
vote
1answer
61 views

Isoprenoid Diphosphate Concentration in Yeast saccharomyces cerevisiae

Isoprenoid Diphosphate(IPP) is an important metabolites which is precursor in lot of secondary metabolites like Dolichol diphosphate, ubiquinone, prenylated proteins and carotenoid (not synthesized ...
1
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0answers
1k views

Bacterial 16S rRNA PCR amplification with universal primers

I am doing an experiment to amplify the 16S rRNA gene from bacteria present in gut contents of fish. After extracting DNA, I perform one-step PCR with universal bacterial primers (27F, 1492R) and I ...
0
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0answers
29 views

Where can I get yeast mutants? [duplicate]

I want to use some yeast mutants to conduct gene functional analysis, and the gene was isolated from plants. Can anybody give me some information regarding the websites or agencies from which I can ...
0
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1answer
81 views

Hypothetically, what is the smallest functional form of human?

Since the my first encounter with doraemon manga, I've been wondering many things, one of them is the small light. Assuming we had an instrument, such as small light, which enabled people to grow and ...
1
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2answers
367 views

Gel electrophoresis question

Leena is a molecular biology student. She purifies two fragments of DNA, 800 and 300 base pairs long. These were obtained from a plasmid after digesting it with HindIII. Each of these fragments has a ...
2
votes
1answer
89 views

What will happen if we expose the brain to an intermittent light?

If a brain is exposed to an intermittent light are specific areas going to fire? If yes, which of them? Is there any experiment about this?
1
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2answers
103 views

Protein purification methods

Which of the following methods would yield the most purified protein fraction? A. Salt precipitation B. Charge separation C. Affinity purification The first one is the most commonly used, is it ...