[_ Old Earth _] Cell Division: Is Evolution Divided?

[Asyncritus]

[FONT=&quot]Mitosis [/FONT][FONT=&quot]

For those who may not know, a cell can divide in two ways. It can use a process called mitosis, or it can use the other method called meiosis.

The mechanics of the two processes are quite startling, and are very clearly designed to carry out their absolutely vital functions accurately.

Cells have to reproduce themselves in order for growth to take place, to repair damage, for simple maintenance and other needed functions. Meiosis produces the extraordinary sex cells, but more on this later.

When they divide, the number of chromosomes, and thus the genes on them must be replicated exactly in the new cells, otherwise damage and destruction will take place. A mutation damages the genetic make up of the cell, and as we have said several times before, such damage is destructive in 99.99% of the cases in which it occurs.

Which is only to be expected. If the plans for say, a car, become damaged in any way, and the construction continues despite the damage, we wouldn’t be too surprised to find the steering wheel up the exhaust pipe, or the engine in the passenger seat! Either way, the car will not function, or at best will be badly impaired.

Continued damage to the plans, does not, or is most unlikely to produce improvement in the car. No matter how many times we tear up and reconstitute the plans for a Honda Civic, we will never get the plans for a Boeing 747.

And there is another problem, the problem of size. A Rolls Royce is not simply a scaled up version of a Honda Civic. It is a completely different animal, whose physics, chemistry and metallurgy are entirely changed. The design of a mud hut cannot simply be enlarged to produce the Empire State Building. It would definitely look a bit odd, for starters.

In the cell, the damage can be of several well known kinds.

1 The chromosome may duplicate itself unnecessarily: so there is one or more than one extra chromosome in the make up.

2 The chromosome may have a section torn off or lost

3 The chromosome may break and rejoin the wrong way round, so instead of the genes being in the order AAABBBCCC, something else appears like CCCAAABBB. This also produces damage, much as if a page of the plans for the car was torn in 3, and the sections glued back in the wrong order.


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[Asyncritus]

[FONT=&quot]In every case there is damage of one sort or another. Beneficial mutations are extremely rare, and never produce new species, far less new genera. Micro-evolution, like the emergence of bacteria resistant to antibiotics, is a very long way indeed from the macro-evolution of a whole new family, or phylum. [/FONT][FONT=&quot]

But back to mitosis.

In a normal body cell, let’s say there are 10 individual chromosomes. These are in pairs, so there are 5 pairs. In order to make sure that the daughter cells have exactly the same number of chromosomes, this remarkable process takes place.

A.A B.B C.C D.D E.E

Each pair of chromosomes copies itself exactly.

A.A B.B C.C D.D E.E becomes

A.A A.A B.B B.B C.C C.C D.D D.D E.E E.E

So for a brief moment, the cell has 20 chromosomes, in 10 pairs. 5 pairs are exact replicas of the other five. The dot in the middle indicates that they are joined at a certain point.

Two structures called centrioles appear, and move to the opposite ends of the cell, and fibres begin to appear: they then join in the middle, believe it or not, to form what is called a ‘spindle’. The nuclear membrane disappears.

Amazingly, the chromosomes arrange themselves at the ‘equator’ of the spindle (across the middle) and are attached to the fibres of the spindle.

The spindle pulls them apart, and they separate, going to the opposite ends of the cell. So at each end of the cell there are now 5 pairs of chromosomes. The original number.

The nuclear membrane reforms round the chromosomes, and the cell pinches in the middle, and two new cells are now formed, each containing 5 pairs of chromosomes: A.A B.B C.C D.D E.E once more.

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[Asyncritus]

There is very clear purpose in every move of this division process.

1 The chromosomes duplicate themselves, as if they knew that the new cell must have a copy.

2 The spindle is constructed, at the right time and in the right place SO THAT it can pull the chromosomes apart from their joint. It is a subject of much research, which is showing much protein involvement in the structure. Protein, remember, cannot be produced without enzymes, and enzymes themselves are proteins.

3 The nuclear membrane dissolves, with the purpose of getting out of the way so the division can take place.

4 The chromosomes arrange themselves at the ‘equator’ of the spindle, the maximum distance away from the centrioles SO THAT the maximum leverage can be exerted on them to separate them. They separate.

5 They move to opposite ends of the cell, SO THAT each new cell has exactly the same number of chromosomes as the original.

6 But number is not enough. Five DIFFERENT chromosome pairs must be in each daughter cell. (For instance, AA AA BB CC DD would be disastrous). This way of doing the division ENSURES that they ARE different.

7 The nuclear membrane reforms when the division is complete, and TO COMPLETE THE PROCESS, the cell wall itself pinches off to make 2 new cells.

At every step of the way, design, foreknowledge and purpose are clearly displayed. The most surprising thing in my view, is that the exact numbers of chromosomes is preserved in each daughter cell. If they weren’t, then chaos would soon result.

Order, purpose, design, and intelligence are displayed in abundance in this process. There is nothing whatsoever left to chance. If it were, there would be, as I have said, chaos in the genetics of the organism, which would result in death, disease or sterility.

The probability of the biochemistry of this process having emerged by chance movement of molecules is ridiculous. The very possibility does not exist. Errors here, and even more so in meiosis, would result in the extinction of life itself.

But we here run up against the old, old evolutionary conundrum. Cellular life could not exist without mitosis, and mitosis could not exist without life. Therefore, life and mitosis could not have come from inert molecules.

God designed them and they appeared together.

 

[Barbarian]

In every case there is damage of one sort or another. Beneficial mutations are extremely rare, and never produce new species, far less new genera. Micro-evolution, like the emergence of bacteria resistant to antibiotics, is a very long way indeed from the macro-evolution of a whole new family, or phylum.

But back to mitosis.

In a normal body cell, let’s say there are 10 individual chromosomes. These are in pairs, so there are 5 pairs. In order to make sure that the daughter cells have exactly the same number of chromosomes, this remarkable process takes place.

A.A B.B C.C D.D E.E

Each pair of chromosomes copies itself exactly.

A.A B.B C.C D.D E.E becomes

A.A A.A B.B B.B C.C C.C D.D D.D E.E E.E

Would you like to see an easy simulation using your idea, that shows how random mutation and natural selection can increase fitness in a population?

If you like, I can show how it could lead to new structures. Want to try it?

 

[Asyncritus]

Would you like to see an easy simulation using your idea, that shows how random mutation and natural selection can increase fitness in a population?

Since random mutation DEPENDS on the already existing processes of mitosis and meiosis, it is difficult to see how the simulation you refer to isn't a major case of question begging.

The whole lot falls flat at this hurdle.

If you like, I can show how it could lead to new structures. Want to try it?

If it can show how mitosis could have appeared, then yes.

 

[Barbarian]

Since random mutation DEPENDS on the already existing processes of mitosis and meiosis

Don't tell the bacteria. They've been doing it for billions of years without it. No nuclear membrane, you know. However, in some bacteria, a primitive sort of mitosis-like process happens.

So the mitosis we see in eukaryotes didn't pop out of nowhere; there are precursors in non-mitotic organisms:

Model of ParAI-mediated segregation of the ParBI-bound origin of chrI. (A) Older, predivisional, cells contain two fully replicated and segregated chromosomes. The origin of each chromosome is attached to the pole by an interaction between ParAI, anchored to an as-of-yet unknown polar protein/structure, and ParBI, bound to the chromosome at the origin-proximal parSI site. (B) At some point, perhaps related to the assembly of the cell division machinery, ParAI nucleates at the forming septum and polymerizes outward as bands or networks of polymers toward both poles. The next round of DNA replication yields sister copies of the origin region, each containing a ParBI–parSI complex. One complex is captured by the ParAI already present at the old pole; the other ParB–parSI complex is captured by the ParAI extending from the closing septum that will become the new pole. (C,D) The completion of cytokinesis produces two daughter cells in which ParBI-bound DNA is being pulled across the cell by the retracting ParAI polymers.

A dynamic, mitotic-like mechanism for bacterial chromosome segregation

If it can show how mitosis could have appeared, then yes.

How about that?

 

[Asyncritus]

Don't tell the bacteria. They've been doing it for billions of years without it. No nuclear membrane, you know. However, in some bacteria, a primitive sort of mitosis-like process happens.

So the mitosis we see in eukaryotes didn't pop out of nowhere; there are precursors in non-mitotic organisms:

Model of ParAI-mediated segregation of the ParBI-bound origin of chrI. (A) Older, predivisional, cells contain two fully replicated and segregated chromosomes. The origin of each chromosome is attached to the pole by an interaction between ParAI, anchored to an as-of-yet unknown polar protein/structure, and ParBI, bound to the chromosome at the origin-proximal parSI site. (B) At some point, perhaps related to the assembly of the cell division machinery, ParAI nucleates at the forming septum and polymerizes outward as bands or networks of polymers toward both poles. The next round of DNA replication yields sister copies of the origin region, each containing a ParBI–parSI complex. One complex is captured by the ParAI already present at the old pole; the other ParB–parSI complex is captured by the ParAI extending from the closing septum that will become the new pole. (C,D) The completion of cytokinesis produces two daughter cells in which ParBI-bound DNA is being pulled across the cell by the retracting ParAI polymers.

A dynamic, mitotic-like mechanism for bacterial chromosome segregation



How about that?

So these prokaryotes don 't have the full mitotic process, but something similar. In any case, I am discussing 'mutations' which drive evolution.

But here's your article:

to date, mitotic-like mechanisms that act on the bacterial chromosome have not been demonstrated. Here we provide evidence that the Vibrio cholerae ParAI and ParBI proteins are components of an apparatus that pulls the origin region of the large V. choleraechromosome to the cell pole and anchors it there.

Where did this abbreviated process come from, B? Did the bacteria figure it out all by themselves?

It's all very well muttering about there being 'precursors'. That's great, but we have the question still before us: where, and how did this 'abbreviated' process arise?

The question here, as I've been showing on this and other threads, is about the fact that these things appear to 'know' what they're doing.

The bacterial cells are reproducing after their own peculiar fashion. Whether you care to call it mitosis or not is up to you.

But the fact remains that they 'know' what they are doing, and in fact do it so well that they've been here since the year dot.

Now to generate or invent such a thing requires 'information' which I choose to call 'instinct' since it is unlearned.

A bacterium cannot generate 'instinct' because it requires 'instinct' to generate that 'instinct' - and so we keep pushing the boundaries back: where did it all begin?

So until you can answer the 2 most fundamental questions in all of biology, you case remaning heavily perforated.

The questions are:

1 How did the instinct arise and

2 How did it enter the genome (if that's where it is).

 

[Barbarian]

So these prokaryotes don 't have the full mitotic process,

Some of them do. A primitive process, using some of the components of eukaryotic mitosis, but not all of them.

In any case, I am discussing 'mutations' which drive evolution.

If you're seriously interested, I can still show you a simulation that illustrates how it works.

to date, mitotic-like mechanisms that act on the bacterial chromosome have not been demonstrated. Here we provide evidence that the Vibrio cholerae ParAI and ParBI proteins are components of an apparatus that pulls the origin region of the large V. choleraechromosome to the cell pole and anchors it there.

Where did this abbreviated process come from, B?

They are apparently derived from simpler proteins that are involved in other cellular functions:
http://faculty.washington.edu/scottjdw/pdfs/jin_curr_biol_2004_p1436.pdf

Did the bacteria figure it out all by themselves?

Bacteria don't think. It's just an advantageous mutation or several over time that account for these slight improvements.

It's all very well muttering about there being 'precursors'. That's great, but we have the question still before us: where, and how did this 'abbreviated' process arise?

Pretty much the way you'd expect. Modification of something else already there. That's how it goes in evolution. Don't guess we'll ever figure all of it out, but every time we learn something, it's evolutionary processes.

The question here, as I've been showing on this and other threads, is about the fact that these things appear to 'know' what they're doing.

People used to think the sun knew what it was doing, going across the sky each day. Eventually we realized that it doesn't.

The bacterial cells are reproducing after their own peculiar fashion. Whether you care to call it mitosis or not is up to you.

Not quite mitosis, is it? Almost there. That's how it works in biology. Nothing brand new, always a modification of something that went before.

But the fact remains that they 'know' what they are doing

No more than a rock knows what it's doing when it rolls down a hill.

and in fact do it so well that they've been here since the year dot.

Very unlikely, seeing as only some species of prokaryotes have evolved the process.

Now to generate or invent such a thing requires 'information' which I choose to call 'instinct' since it is unlearned.

At this level, it's just chemistry. Do youi think a plant instinctively turns to the sun, or is that just chemistry?

A bacterium cannot generate 'instinct' because it requires 'instinct' to generate that 'instinct' - and so we keep pushing the boundaries back: where did it all begin?

Darwin suggested God just created the first living thing. If so, it wouldn't matter to evolution, which isn't concerned about the origin of life. It just describes how existing life changes.

If you believe the Bible, the Earth brought forth living things. Scientists call it "abiogenesis." Is that good enough for you?

The questions are:

1 How did the instinct arise and

The evidence says mutation and natural selection.

2 How did it enter the genome (if that's where it is).

Mutation.