4
votes
1answer
93 views

Is there a cheap and easy way to check for potentially unsafe UV exposure?

My lab has an older large Fotodyne tabletop UV transilluminator for visualizing gels. It has a UV blocking cover that hopefully reduces UV that passes through, but I've always been suspcious as to ...
5
votes
1answer
355 views

X chromosome “weight”?

According to Wikipedia, the X chromosome has approximately 153 million base pairs, while the Y chromosome has only 60 million base pairs. Thus, the difference is roughly 93 million base pairs. My ...
7
votes
1answer
359 views

When do most mammals mate?

Is one part of the day more prevalent then other when it comes to mammal animals mating? Is there an aggregating study that has been done to see if these living beings in nature mate mostly during day ...
2
votes
1answer
262 views

What is the structure and function of chromosomes during interphase?

Ok, it seems to be easy but I have probably ignored something by accident. Interphase is the phase where things are growing and the preparation for cell division happens. Its stages G1, S and G2. DNA ...
6
votes
2answers
605 views

What is the main general difference between Mitosis and Meiosis?

I found such a clause: The general principle is that mitosis creates somatic cells and meiosis creates germ cells. However, I cannot agree. Each gametogonium needs to go through mitosis before ...
18
votes
3answers
5k views

What causes fingerprints to form and why is the pattern formed unique?

I've found research that suggests that the reason we develop fingerprints is because they aid us with feeling surfaces (Scheibert, et al. 2008) and not to increase friction and help with the gripping ...
14
votes
4answers
1k views

Can two humans with 44 chromosomes produce viable offspring?

It is known that there are very few individuals having 44 chromosomes, not the usual 46 chromosomes. One example is a male in China: the first article, the second article. The other is a female in ...
12
votes
2answers
335 views

Is there any reason for the variation in mitochondrial DNA size?

As my textbook An Introduction to Genetic Analysis points out, yeast mitochondrial DNA has approximately 78 kb of genetic data, while the human mitochondrial DNA contains 17 kb. Is there any evolution ...
12
votes
1answer
2k views

How does a plant grow before photosynthesis is possible?

During photosynthesis, a plant translates CO2, water and light into O2. I assume the carbon C is further used for the growing process. I wonder how the plant grows before the time where photosynthesis ...
4
votes
2answers
489 views

What's the advantage of autocrine signalling?

In the antibody-mediated immune response, when the helper T cell gets activated by the costimulus (IL-2 and TNF-α secreted by the APC) which in turn produces IL-2, IL-2 acts in an autocrine manner. ...
18
votes
3answers
11k views

Why do mammalian red blood cells lack a nucleus?

How did the red blood cell in humans get to lose its nucleus (and other organelles)? Does the bone marrow just not put the nucleus in, or is it stripped out at some stage in the construction of the ...
8
votes
1answer
182 views

Which organism has the sharpest vision?

Which organism has the sharpest vision in terms of distance and spectrum. Please propose any other useful measure.
7
votes
2answers
4k views

Mitosis in human body

I've heard that stomach lining has the fastest reproducing cells and the brain has the slowest. Where in the human body does mitosis occur and at what rates do these cell reproduce? Is there a chart ...
3
votes
1answer
250 views

Where does meiosis II of oogenesis end exactly in tuba uterina - uterus?

I know that metaphase II ends at ampulla tuba uterina, but I am not completely sure where the telophase II ends. Is it in the triangular section of cervix uterii? I just have an intuition that the ...
6
votes
1answer
247 views

Which organisms have the neuroanatomy Roger Penrose supposes play a role in consciousness?

In The Road to Reality, Roger Penrose suggests that certain brain structures might play a role in consciousness Most particularly, lattice neuronal microtubules, as originally suggested by ...
2
votes
1answer
127 views

Why are Birds and Reptiles with abundant yolk sac polyspermic?

I was given an explanation that birds and reptiles are polyspermic because they have an abundant yolk sac. But how does it explain the thing? Chicken as an adult is not using in my opinion yolk as an ...
10
votes
2answers
372 views

Why does cyanide inhibit CuZnSOD, but not MnSOD or FeSOD?

Different types of superoxide dismutase (SOD) contain different metal ions (Zn, Cu, Mn, Ni, or Fe), all of which allow them to catalyze one reaction, dismutation of superoxide anion, O2−. Cyanide can ...
4
votes
1answer
8k views

What factors affect the rate of transpiration in plant leaves?

I'm trying to get my head around factors which affect transpiration in leaves. For example, how would applying petroleum jelly to the surface of plant leaves affect their rate of transpiration? I ...
7
votes
3answers
358 views

Can protein structure be determined by X-Ray Diffraction in a single image?

I'm reading about the use of x-ray crystallography to determine protein structure. According to my book, data is collected at 30-360 angles (dependent on the symmetry of the protein). An illustration ...
5
votes
1answer
952 views

What is the distinction between F' plasmid and R plasmid?

Is there a difference between an F' plasmid that has taken up a chromosomal gene that conveys antibiotic resistance, and an R plasmid? Is a bacterium containing an R plasmid and yet lacking an F+ ...
11
votes
3answers
447 views

How did the huge dinosaurs cope with gravity and loads on bones, etc.?

It's very costly to be a huge animal. Your mass grows in cube when you scale up, but you still only have two/four legs to support the same weight. This increases the pressure that your body needs to ...
7
votes
1answer
330 views

Why do people look different after a long sleep?

What happens during a long sleep that makes people look odd when they have just woken up? Why doesn't the same phenomenon occur in the case of a person who lies down for an extended period of time, ...
8
votes
2answers
2k views

Are there any motile plants?

There are numerous examples of sessile animals (sponges, barnacles etc.) but are there any examples of motile plants? If not, why not? Surely mobility would have conferred an evolutionary advantage to ...
5
votes
1answer
146 views

When does Coelom form exactly?

Related to my other question. I know that the coelom is derived from mesoderm. Coelom seems to form during organogenesis within 3rd and 8th week of embryogenesis. However, that answer is not either ...
4
votes
1answer
2k views

Do humans have Coelom?

Kimball Biology 5e says Coelom is the main body cavity of many animals. It is lined with an epithelium derived from mesoderm. Gilbert Embryonal Biology 9e says Coelom is the space between ...
10
votes
1answer
311 views

Is there are evolutionary explanation for why humans and primates are ticklish? How might it have evolved?

Tickling is a rather interesting phenomenon: When humans or apes are touched in certain areas like the armpits or sides, we respond with laughter AND frantic attempts to stop the assault. Obviously ...
9
votes
1answer
1k views

Are human chromosomes connected or separate molecules?

Do the 46 human chromosomes form a single unbroken DNA helix? Or is it rather that a human's genome consists of 46 disconnected helices? If it is the former, does the common numbering scheme for ...
9
votes
1answer
110 views

Have there been any positive public health effects due to UV lights?

Occasionally, in hospitals and in eating establishments in the US, they have industrial grade UV lights in sconces attached to the wall (though they seem to be less prominent as the years go by). I ...
4
votes
1answer
2k views

What are differences between formation of embryonic disc in chick and mammal embryo?

Exam question which got lowest average points in my university: 1/5 average. No markscheme available so my attempt below. I assume that embryonic disk prefers to germ disk such that Formation prefers ...
6
votes
1answer
938 views

What hydrolyses aspirin within the digestive tract and blood stream?

I have had some further thoughts after my previous question regarding the buccal delivery of medication. The active compound in aspirin (acetylsalicylic acid or systematically 2-Acetoxybenzoic acid) ...
8
votes
1answer
68 views

Are homozygous carriers of the CCR5-Δ32 allele fully immune to all known strains of HIV?

Or is there documented evidence of even one homozygous carrier contracting HIV and staying infected?
17
votes
3answers
720 views

How long can I store extracted RNA?

If I extract RNA from a (leaf tissue) sample using a one-step phenol:chloroform extraction, how long can those samples be stored at -80°C? And how many times can I defrost and refreeze them before ...
9
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
13k 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
202 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
109 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
369 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
123 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
10k 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
459 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
172 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
103 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
4k 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
860 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 ...

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