7 votes

How can neurons divide without centrioles?

You talk about memory loss. The hippocampus is involved in the formation and storage of memories and indeed one of the few places in the brain where new neurons are formed. The formation of new ...
AliceD's user avatar
  • 52.4k
6 votes

How do stem cells produce 200 billion new blood cells every day? Does 1 stem cell division result in production of just 1 blood cell or many?

The hematopoietic stem cells are quite rare, and each progenitor cell produced by a stem cell gives rise to a large number of red blood cells (and other blood cell types). I'm not sure if the precise ...
Roland's user avatar
  • 5,705
5 votes
Accepted

Why are humans only so tall/large?

The question is a bit vague but I will take it to mean the following Why does it (the body) stop in terms of height or physical mass when it can still keep on growing? The answer is physics, ...
JayCkat's user avatar
  • 2,926
4 votes

How are germ cells not reduced in number?

In case of gametogenesis (let us talk about spermatogenesis) gametes are formed from meiotic division of Primary spermatocytes. In Primates Primary spermatocytes are cells that that are formed from ...
Tyto alba's user avatar
  • 8,782
3 votes
Accepted

Names of different cyclins

Biological nomenclature can be impenetrable. Almost certainly, at some point in history, there were cyclins designated with these letters. Researchers would have discovered apparently novel cyclins ...
canadianer's user avatar
  • 17.7k
3 votes
Accepted

Genetic information storage and the extent to which it controls appearance/structure

The common phrase I've heard is "DNA isn't a blueprint, it's a recipe". More specifically, the nucleotides in DNA correspond to which proteins get made (coding DNA) and when and where (regulatory DNA)....
Oosaka's user avatar
  • 3,245
3 votes

How are germ cells not reduced in number?

"How are germ cells not reduced in number?" It does happen. Germ cells do eventually run out. It is called menopause in women. And age related infertility in men. As for your question of where do ...
JayCkat's user avatar
  • 2,926
3 votes

How far is stem cell research from being to generate a new organ?

Sperm can already be generated using stem cells http://blogs.discovermagazine.com/d-brief/2016/02/25/scientists-grow-working-sperm-from-stem-cells/#.V-UADBV94o8 Also, heart, liver and kidney cells as ...
alec_djinn's user avatar
  • 3,108
3 votes
Accepted

Why doesn't cellular, replicative senescence (or the hayflick limit) constrain the normal development of an organism?

You pretty much have answered your own question. It is a math problem. Cells are burning up their telomeres during fetal development onward but the cells are multiplying exponentially in number. But ...
JayCkat's user avatar
  • 2,926
2 votes
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Contact Inhibition of Cell Division: Signaling Pathway

How does the mitotic entry machinery roughly respond to cell volume? This is a broad question but luckily there is one article that addresses this precise question in detail. However, it is very ...
WYSIWYG's user avatar
  • 35.6k
2 votes

How do cells determine what size to grow to before dividing?

All eukaryotic cells have 'checkpoints' during their cell cycle (1)1. They will only commit to cell division or the next phase of mitosis until all requirements have been fulfilled. The cell needs to ...
mimat's user avatar
  • 1,425
2 votes
Accepted

What organism has the longest Hayflick Limit?

The Hayflick limit is generally associated with telomere length. Human telomeres are a little on the long side as species go, but are not extraordinary. Many species of mice, and other rodents, have ...
iayork's user avatar
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2 votes
Accepted

How long does each of the stages in meiosis take?

If you take a look at the figure directly above the image you posted in the link you posted, you'll see a very different set of figures. It turns out, time spent in different phases of the cell ...
De Novo's user avatar
  • 8,791
2 votes
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Can a viable embryo develop from the fusion of two egg cells?

Yes, it is possible to make a zygote from two ovules. Other more complex scenarios are possible as well. You might want to read this cbc article. If the two ovules came from the same organism, then ...
Remi.b's user avatar
  • 68.1k
2 votes
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Why do chromosomes uncoil back to chromatin after cell divisions?

The condensed form of DNA that exists during cell division is tightly wound and therefore unavailable to the enzymes and transcription factors that interact with and read DNA. So, if chromosomes are ...
acvill's user avatar
  • 8,296
2 votes
Accepted

What are chiasmata?

We need to make a distinction between the genetic map of a chromosome, which is usually built up from meiotic recombination frequencies between linked genetic markers, the physical map of a chromosome,...
mdperry's user avatar
  • 3,517
2 votes
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Why is a cell in anaphase (without a nuclear envelope) be considered as a eukaryotic cell?

It is still considered a Eukaryotic cell because the daughter cells and mother cell are both Eukaryotic; the chromosomes will condense and be contained in a Nucleus after Telophase and Cytokinesis. ...
Yashas Ravi's user avatar
2 votes
Accepted

Could someone explain how chromosomes are counted here?

Like @mgkrebbs commented, the left poster shows a total of 8 chromosomes, but only 4 pairs of chromosomes. I would dare say that you are right and that the poster is wrong. The left has 8 chromosomes, ...
Zo-Bro-23's user avatar
  • 581
2 votes

Why does Meiosis produce 4 daughter cells instead of 2? Won't splitting the initial diploid cell into two haploid cells be easier?

here is what I think why cells evolved to do meiosis like as it is now and not like you mentioned. First I will try to tell you briefly (not in detail) how crossovers are made and how they ensure the ...
AfraidZigma's user avatar
2 votes
Accepted

When do retinal cells stop differentiating?

why do eye conditions like retinoblastoma develop primarily in infants? One explanation is that infants grow fast. In general, each cell division is a risk of breaking/losing chromosomes. Breaks need ...
markur's user avatar
  • 1,769
1 vote

How many times have the cells in a human body divided?

The supplemental material of the paper that Dirigible references in a comment to my question gives a rough estimate of these values. If I understand their simple model correctly, then we can estimate ...
tparker's user avatar
  • 717
1 vote

Why do chromosomes uncoil back to chromatin after cell divisions?

It’s happening because genetic information from DNA can be read only if it’s in the chromatin form, it can’t be read from chromosomes and so the cell can’t fulfill its functions. But if it’s need to ...
Eviline's user avatar
  • 11
1 vote

Name/term for mechanisms by wich the relative size/number of cells of some tissue/organ are preserved

You are referring to organ “scaling” and “allometry”.
J--'s user avatar
  • 428
1 vote

Name/term for mechanisms by wich the relative size/number of cells of some tissue/organ are preserved

'Eutely' is the term used for organisms with a fixed number of somatic cells. I'm not aware of any term for sub-organismic structures.
Quercus Montana's user avatar
1 vote
Accepted

DNA replication - 2 new strands or original (parent) and child?

Via: https://en.wikipedia.org/wiki/Semiconservative_replication Semiconservative replication describes the mechanism of DNA replication in all known cells. It derives its name from the fact that it ...
Alex Reynolds's user avatar
1 vote

Does a cell suspend or exit cell cycle at G0?

It is actually suspend and yes the words do differ. This is because the cells that enter the G0 stage is not actually exiting the cell cycle because when situation demands it will divide. It is ...
June's user avatar
  • 21
1 vote
Accepted

How do adult differentiated somatic cells divide?

There is no known alternative mechanism of proper cell division apart from mitosis and meiosis in animals. I think this is an unfortunate phrasing where the author is trying to introduce the term "...
Armatus's user avatar
  • 7,660
1 vote

When two amoeba cells form from one amoeba, does spindle fibers form?

Amoebas undergo binary fission, which is a much more simplistic process than mitosis. In binary fission, the duplicated chromosomes simply separate as the cells is pulled apart. There are no spindle ...
LizFerg's user avatar
  • 146
1 vote
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Which is the correct term haploid daughter cells or haploid parent cells?

"Parent" and "daughter" terminology is indeed relative. Any parent cell has been a daughter at some point. However, in the case of the zygote there is no "parent" strictly speaking since it is the ...
alec_djinn's user avatar
  • 3,108
1 vote

Can a viable embryo develop from the fusion of two egg cells?

You're describing chimerism (distinct genotypes in a single organism; in animals, this arises when two fertilized eggs merge). This article suggests that "microchimerism" can occur during pregnancy ...
Bruce Kirkpatrick's user avatar

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