8
votes
2answers
2k views

How do I clean and calibrate pipettes, and how often should I do it?

I work in a lab where all the pipettes are shared. We often have visiting students who come and use the pipettes for a short project. So when I work with them, they might have been handled by other ...
9
votes
1answer
12k 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?
6
votes
2answers
192 views

What is the eye muscle status when you stare at distant view through a glass wall?

The book said when you look at object close to you, the eye muscles contract and vice versa. I wonder what will be the status of the eye muscles when I stare at distance view (such as a mountain) ...
10
votes
2answers
108 views

Why do cucurbits produce so much fluid when their stems are cut?

When carrying out some germination tests on species in the Cucurbitaceae, I notice that young plants of this family produce a lot of clear fluid when they are dissected. Most plants I dissect do not ...
19
votes
3answers
1k views

Is it necessary to conduct a power analysis before beginning an experiment?

I know that power analysis is the statistically valid way to ensure you use the correct numer of samples or repeats in an experiment. But I have never seen any biologist actually conduct a power ...
8
votes
2answers
3k views

Why should I degas my gel solution for polyacrylamide gels?

In protocols for polyacrylamide gel electrophoresis (PAGE) I often see instructions to degas the gel solution by putting it under vacuum for 10-15 minutes before polymerizing the gel. I usually ...
10
votes
1answer
368 views

Does electricity cause damage on a cellular level?

As I understand it the mechanism of death when a mammal is electrocuted is that the current disrupts the SAN/AVN in the heart causing it to fibrilate or arrest. That's on a macro scale, however. ...
9
votes
1answer
122 views

Chicken Genome what are the LGE 'chromosomes'?

The chicken genome identifies two "LGE" sequences in the chicken genome. Are these distinct chromosomes or some highly variable sequence from the genome that is put in a separate sequence? I'm ...
4
votes
3answers
9k views

Does Human Female Meiosis II occur after fertilization with sperm?

I am reading the answer and I am getting confused by the sentence: At the end of meiosis I females have two daughter cells and meiosis II only occurs if and when fertilization occurs by a sperm ...
2
votes
1answer
457 views

What does entering of sex chromosomes to gametes mean during meiosis I?

I am reading one answer about meiosis: During meiosis I, the sex chromosomes separate and enter different sperm or egg cells (gametes). I assume that sex chromosomes refer here to homologous ...
1
vote
1answer
171 views

Is this mammalian embryo blastocyst, gastrula or only phase between them?

The picture shows the formation of early blastocyst and late blastocyst. The middle embryo has embryoblast. My professor says that blastocyst in general has embryoblast and trophoblast. Embryoblast ...
11
votes
2answers
245 views

What is the tRNA gene copy variation between different yeast strains?

I just started working on predicting steady-state protein levels from different codon usage bias measures. I have whole-genome sequences (it's NGS data) from different strains of S. cerevisiae and S. ...
7
votes
0answers
102 views

How reversible is DAT upregulation from long-term ADHD medication use?

A mechanism for ADHD stimulant medication tolerance has now been found. See http://neurosciencenews.com/adhd-medication-patient-brains-adapt-dat/. Here's the thing though: what exactly is the ...
4
votes
1answer
328 views

Does Amphibian embryo's blastocoel become a primitive yolk sac without yolk?

The mammalian blastocoel becomes yolk sac without yolk according to my professor. I have not found any evidence that such a thing happens in amphibians like frog. I need to be able to compare and ...
5
votes
1answer
87 views

What is the total number of rounds of cleavage during mammalian embryonic development?

That for frog is 12, but what about mammalian embryos? I cannot find the exact number anywhere.
6
votes
1answer
3k views

Does consuming sodium benzoate (preservative E211) cause problems during pregnancy?

There seems to be strong evidence to support the claim that sodium benzoate (E211) causes hyperactivity in young children, e.g. Bateman et al. (2004) and McCann et al. (2007). This leads me to ...
7
votes
2answers
294 views

Can a living organism run on electricity?

Each time I'm too lazy too cook I think it'd be cool to be able to just plug myselt into an outlet. Yet I know it is not possible - I need amino acids and a lot of other stuff that electricity can't ...
6
votes
1answer
854 views

What is the average Leg-to-Foot Length/Width Ratio?

I'm making a program that estimates a probable size (widest width and longest length) for a human's foot given the length and width of the leg to which it is attached. However, try as I might, I can't ...
59
votes
2answers
1k views

How many times did life emerge from the ocean?

Evolution is often mistakenly depicted as linear in popular culture. One main feature of this depiction in popular culture, but even in science popularisation, is that some ocean-dwelling animal sheds ...
28
votes
3answers
2k views

Why is polyploidy lethal for some organisms while for others is not?

Polyploidy is the multiplication of number of chromosomal sets from 2n to 3n (triploidy), 4n (tetraploidy) and so on. It is quite common in plants, for example many crops like wheat or Brassica forms. ...
5
votes
3answers
1k views

Why does so much variation exist within species?

My last phrasing of this question did not go down well, so I will try again. The genotype of species is not always the same. If you ask yourself why not all of these possible expressions except one ...
12
votes
1answer
3k views

How does Golgi's neural histological stain work?

What is known about the targets of Golgi staining of neurons? Are larger neurons more likely to be stained? Are specific cell types more susceptible than others? The current wikipedia article says ...
15
votes
2answers
2k views

Harmless virus?

Is it possible for a virus to live symbiotically with its host? Is the human body plagued with viral infections that do negligible harm, or even serve a beneficial role?
12
votes
1answer
3k views

Why does scar tissue change color?

I was wondering why, when you are cold, scar tissue turns bluish or purple while original skin stays the same color. The only thing I can think of, is that maybe scar tissue gets less circulation ...
3
votes
1answer
170 views

How do you see the stage of the second meiotic arrest in oogenesis in the given video?

My old question raised this new question. After reading this page I can say now that metaphase is the stage in which the second meiotic arrest occurs within oogenesis: The oocyte is arrested again ...
7
votes
4answers
1k views

If I put a cup over a spider, and leave it there for a day, will the spider survive?

Will it travel more slowly since it hasn't had food for a day? What if I left the cup there for longer?
7
votes
1answer
174 views

Does cooking ginger reduce its anti-nausea effect?

There seems to be strong evidence to support the hypothesis that eating ginger helps reduce nausea e.g. during pregnancy (e.g. Vutyavanich et al.). It seems that gingerol is the active ingredient in ...
9
votes
1answer
760 views

Why do some plant species have lobed leaves, while similar species in the same habitat don't?

Some plants have lobed leaves, like the English oak (Quercus robur), while other plants growing the same deciduous woodland habitats, and very often growing alongside oaks, such as the European beech ...
6
votes
1answer
156 views

What's a good reference for choosing histological staining chemicals?

It's often difficult to find the appropriate or best stain to use when I want to examine a new type of tissue. I think that's partly because many histological techniques were developed a long time ...
10
votes
2answers
4k views

How do I clean phenol contaminated RNA without losing any of the sample?

I recently extracted RNA from developing plant leaves for the first time, as part of a very long and intensive experiment. The samples were extremely precious because of the amount of effort that went ...
5
votes
1answer
609 views

How does water buffer a sudden drop in temperature?

A property of water is that it is slow to heat and cool. According to my biology book, some energy from an increase in temperature would spent breaking hydrogen bonds, so that temperature does not ...
7
votes
2answers
554 views

What effect does ambient temperature have on the cardiovascular system?

I am sorry if this is not appropriate for this site, but I think it fits so I am asking it here: I went for a run yesterday, and it was about -8 degrees Celsius. I was wearing a couple pairs of ...
16
votes
1answer
734 views

Do insects' muscles become stronger with exercise?

I am curious to know if insect muscles become stronger with exercise, because I have seen many insects get tired out, but I have never seen one get stronger. They always seem to become permanently ...
11
votes
3answers
457 views

Is Behe's experiment (evolving the bacterial flagellum) plausible in the lab?

[Warning: this question is motivated by a prominent proponent of "intelligent design": Prof. Michael Behe. I'm not interested in debating creationism.] According to Wikipedia[1]: In Darwin’s ...
5
votes
1answer
285 views

How do you turn a minimal CIF description into a complete one?

I have a CIF file that I downloaded from the PDB, but if I try to use it in Coot, it complains that it is not a complete CIF definition. This page provides a batch script that I may be able to tease ...
6
votes
1answer
2k views

What cells would have the CD3 marker on them (other than T-cells)

Do you know of any peripheral blood mononuclear cells that would express any amount (beit low or high) of CD3 on their surface (other than T-cells)?
6
votes
2answers
278 views

What is a good Non Fluorescent DNA Dye?

Can anyone suggest a dye which specifically targets DNA, but is not fluorescent? (We plan to mark DNA before observing it with RAMAN-Spectroscopy. Because of the weak Signal even a low emission would ...
12
votes
5answers
299 views

Is it the case that all changes in phenotype during life are not inheritable?

This came up in a talk with a friend. I wanted to clear this doubt. I've read about it before and did again after her remark (my thoughts didn't change: her concept is Lamarck's, not Darwin's), but ...
22
votes
1answer
478 views

How long will a vegetable live for after being harvested?

I understand this might depend on the types of vegetables, but is there an average or studied specifics? Does it die immediately? Is there a way to precisely diagnose death in plants? If so, what are ...
6
votes
1answer
279 views

Why are beta-galactosidase proteins overexpressed in senescent cells?

Wikipedia explains that it's a hypothetical hydrolase enzyme that catalyzes the hydrolysis of β-galactosides into monosaccharides only in senescent cells. I'm just wondering - what causes it to be ...
5
votes
1answer
161 views

Why isn't the p16-INK4a gene involved in apoptosis expressed in heart or liver tissues?

New York Times article explains how killing p16-INK4a positive senescent cells can help keep the surrounding cells vigorous. So here's my question: why is p16-INK4a expressed in most cells other than ...
4
votes
1answer
738 views

How do caspase proteins kill a cell?

Wikipedia just says... The active effector caspases then proteolytically degrade a host of intracellular proteins to carry out the cell death program. Okay, but what parts of the cell do they ...
7
votes
1answer
126 views

How exactly does long-term tension (over months) build up in the ligaments, tendons, muscles?

And is there any basis for believing that massage relieves that tension?
-3
votes
2answers
2k views

At what stage of meiosis does “first meiotic arrest of oogenesis” occur?

An exam question asked what stage of meiosis corresponds with "first meiotic arrest of oogenesis". I can't work out the answer from the wiki page - can anyone explain which step this refers to?
8
votes
1answer
492 views

Why do dendritic cells have CD4/CD8 on their surface?

Why do dendritic cells have CD4 or CD8 antigens on their surface? What is their function without the presence of a T-cell receptor?
4
votes
1answer
112 views

What evidence gives clues to the physiological basis for conversion disorder?

Conversion disorder has a set of DSM diagnosis criteria, which, among other things, includes ruling out all neurological disease. However, as the media has shown us (and one could argue a biased ...
10
votes
2answers
5k views

Does an annealing temp higher than primer's Tm contribute to primer dimer?

I am attempting to reproduce results from a number of journal articles all referring to the same SNP. In doing this I'm using the same primer set outlined in the articles. When I attempted a run the ...
11
votes
2answers
290 views

What are the limitations to current nucleotide sequencing technologies?

Using the Illumina platform, it is cheap and (relatively) easy to sequence huge amounts of DNA or RNA. There are various other platforms out there (Roche/454, SOLiD, PacBio, Ion Torrent) each with ...
7
votes
1answer
64 views

How are whole Haplotypes for Sequencing isolated?

Is it possible to reliably isolate and amplify DNA from individual sperm and/or eggs (from a fish)? I'd imagine that the small amount of DNA would make the PCR a bit wacky. We've considered ...
9
votes
1answer
150 views

Is it correct to regard archeaic humans (i.e.n Neanderthals and Denisovans) as distinct species to Homo sapiens?

There is increasing evidence (e.g. here) that Homo sapiens interbred with contemporary homonins such as Homo neanderthalensis and the "Denisovans". Although these homonins do show differences in their ...

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