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Human Eggs Have 46 Chromosomes. Not 23 (Page 1)

Many pl'ers posts recently have been trying to make the point that a sperm and egg alone are vastly different in value (i.e. much less value) from the united sperm and egg, which they claim is a person, or a child.

Personally, I cannot see the huge difference in value from sperm and egg sitting next to each other, vs. sperm and egg touching each other. I think sperm and eggs are just as valuable as a united sperm and egg (zygote).

Many pl'ers claim that it is because sperm and eggs have only half the chromosomes needed for an embryo to develop, which in turn becomes a fetus, and so on. But what they don't know is that before a gamete (sperm or egg) gets half the number of chromosomes, each has the full number (46).

It is only through meiosis (which finishes only after fertilization in the egg), that the chromosome number gets halved in an egg.

This thread discusses the uses of an unfertilized eggs in making embryos and getting stem cells, which is exactly like using fertilized eggs for the same purpose:


Embryonic stem cells made from unfertilized eggs:


Quote:

No fertilization necessary
NOVA scienceNOW: Let's start with the basics. Just what is "parthenogenesis?"

Kiessling: Parthenogenesis is the term that's applied to an egg that activates spontaneously on its own. This is relatively common in women. Eggs activate and often form cysts or benign tumors in the ovary. Those activated eggs begin to divide, and they look like embryos at the early stages. They form blastocysts with stem cells inside.

NOVA scienceNOW: So you're looking at this as a way to produce stem cells for therapy? Give me an example of how it could work.

Kiessling: Take a young woman with Type 1 diabetes. She could donate her eggs. The eggs then could be activated artificially in the laboratory without being fertilized. Those eggs would develop to the blastocyst stage, stem cells would be derived, and those stem cells—her own stem cells—could be used to treat her Type 1 diabetes.

NOVA scienceNOW: Is this type of treatment just theoretical, or have there been animal studies?

Kiessling: It's interesting. The only stem cells that are being used right now to treat Parkinson's disease in monkeys is a line of stem cells that were developed from an unfertilized monkey egg—an egg that went through parthenogenesis. The line of stem cells that was developed from that monkey egg has proven to be as valuable and as robust as stem cells from leftover fertilized human eggs [from fertility clinics].

NOVA scienceNOW: It's surprising that parthenogenesis hasn't gotten more attention in the media.

Kiessling: It really hasn't been discussed. It's also surprising that parthenogenesis has not received much attention even from the research community.


Read more at:



http://www.pbs.org/wgbh/nova/sciencenow/32 09/04-alternative.html
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First Helper User Profile Georgia59
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replied September 21st, 2007
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Why is this surprising?

Every cell in our body has 46 chromosomes. EVERY cell.

Sperm and egg cells have less to be able to make a baby. Yes, for egg cells this may happen later on, but it still happens.

So with that argument- any cell in our body is as important as a human baby. I don't think you're going in the right direction here, sorry to say.....
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replied September 21st, 2007
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Re: Human Eggs Have 46 Chromosomes. Not 23
futureshock wrote:
Many pl'ers posts recently have been trying to make the point that a sperm and egg alone are vastly different in value (i.e. much less value) from the united sperm and egg, which they claim is a person, or a child.

Personally, I cannot see the huge difference in value from sperm and egg sitting next to each other, vs. sperm and egg touching each other. I think sperm and eggs are just as valuable as a united sperm and egg (zygote).

Many pl'ers claim that it is because sperm and eggs have only half the chromosomes needed for an embryo to develop, which in turn becomes a fetus, and so on. But what they don't know is that before a gamete (sperm or egg) gets half the number of chromosomes, each has the full number (46).

It is only through meiosis (which finishes only after fertilization in the egg), that the chromosome number gets halved in an egg.


I have a bio question because I do not remember...

Aren't women born with all the eggs they are ever going to have...and aren't those eggs haploid from the getgo?

I do not think that meiosis finishes post fertilization in the egg...the egg starts out haploid and after fertilization with the haploid sperm it becomes diploid...

Right? *shrugging smiley*
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replied September 21st, 2007
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I'll dig out my biology notes....
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replied September 21st, 2007
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Didn't want to dig through the textbook so I just wiki'd gametes.

"In higher animals, ova are produced by female gonads (sexual glands) called ovaries and all of them are present at birth in mammals, and mature via oogenesis."

So yeah.... they're all there and ready to go- with 23 nice happy haploid chromosomes (half of the set, like we've been saying) when you're born.
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replied September 21st, 2007
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I still don't get the point though. Somatic (body) cells all have 46 and no one's trying to say that that's a baby....
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replied September 21st, 2007
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Re: Human Eggs Have 46 Chromosomes. Not 23
Birch wrote:


I have a bio question because I do not remember...

Aren't women born with all the eggs they are ever going to have...and aren't those eggs haploid from the getgo?

I do not think that meiosis finishes post fertilization in the egg...the egg starts out haploid and after fertilization with the haploid sperm it becomes diploid...

Right? *shrugging smiley*


That's what I thought too. That's what all my research says. This guy wants to reach waaaay back to the fetal stage when yes, the female eggs were diploid. Then they divided. Then the girl was born.
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replied September 21st, 2007
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Hey wait... I did dig out my biology text and figured it out.

We are born with all our eggs, but they are diploid ( chromos) when we're born. They hibernate until we start ovulating, and a few (or one I guess) matures each month partway through meiosis so it is haploid when it is ovulated, and then finishes the process if it gets fertilized, joining with the sperm chromos.

So a little of both. They are diploid when we're born.

Just like the rest of our cells. Confused

From my bio textbook.
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replied September 21st, 2007
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This Topic Contains Harmful Content...
Personally, this whole topic is actually misinformation, or at least the title is. Because of this, I don't think it should be left on the forum.

Humans' mature reproductive cells (eggs and sperm) ARE HAPLOID people. Please don't listen to this guy.

As for men, sperm is constantly produced, so in that case, there may be a diploid cell sitting in each testicle popping out more HAPLOID sperm.

Eggs from birth and mature sperm are HAPLOID. Not diploid, as this OP wants you to believe.

Georgia brings up the actual clear point.

The two items that meet each other to make a baby... are haploid.

Does it really matter if there are diploid cells in the ovaries and testicles?? I don't see how that matters. The eggs that both pro-lifers and pro-choicers care about are the mature ones that have ovulated. The sperm that pro-lifers and pro-choicers are about are the mature ones headed down the vas-defrens.
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replied September 21st, 2007
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No op is right.

Somewhat right.

My question is, why does it matter??
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replied September 21st, 2007
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Georgia59 wrote:
No op is right.

Somewhat right.

My question is, why does it matter??

He's very misleading and I don't like it. He makes it sound like two cells (sperm and egg) both have 46 chromosomes and that those are the specific cells that meet up to make a baby!!
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replied September 21st, 2007
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Eiri wrote:
Georgia59 wrote:
No op is right.

Somewhat right.

My question is, why does it matter??

He's very misleading and I don't like it. He makes it sound like two cells (sperm and egg) both have 46 chromosomes and that those are the specific cells that meet up to make a baby!!


I agree. This is a weird topic.
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replied September 22nd, 2007
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Georgia59 wrote:
Why is this surprising?

Every cell in our body has 46 chromosomes. EVERY cell.

Sperm and egg cells have less to be able to make a baby. Yes, for egg cells this may happen later on, but it still happens.

So with that argument- any cell in our body is as important as a human baby. I don't think you're going in the right direction here, sorry to say.....


I don't think every cell is as important as a human baby, I think every cell is as important as the cell made when sperm meets egg.
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replied September 22nd, 2007
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Georgia59 wrote:
Hey wait... I did dig out my biology text and figured it out.

We are born with all our eggs, but they are diploid ( chromos) when we're born. They hibernate until we start ovulating, and a few (or one I guess) matures each month partway through meiosis so it is haploid when it is ovulated, and then finishes the process if it gets fertilized, joining with the sperm chromos.

So a little of both. They are diploid when we're born.

Just like the rest of our cells. Confused

From my bio textbook.


GOOD!

Pl'ers try to say eggs and sperm aren't "babies" by themselves because they only have 23 chromosomes each. Right?

Do they or do they not say this?
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replied September 22nd, 2007
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Eiri wrote:
Georgia59 wrote:
No op is right.

Somewhat right.

My question is, why does it matter??

He's very misleading and I don't like it. He makes it sound like two cells (sperm and egg) both have 46 chromosomes and that those are the specific cells that meet up to make a baby!!


No, that's not what I said.

The egg cells are diploid until fertilization.
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replied September 22nd, 2007
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futureshock wrote:
Eiri wrote:
Georgia59 wrote:
No op is right.

Somewhat right.

My question is, why does it matter??

He's very misleading and I don't like it. He makes it sound like two cells (sperm and egg) both have 46 chromosomes and that those are the specific cells that meet up to make a baby!!


No, that's not what I said.

The egg cells are diploid until fertilization.

Exactly, you are misinformed, or lying, or just plain confused.

The egg cell is HAPLOID from around the time of ovulation all the way until fertilization. What do you think happens!?

What, a 46 chromosome egg pops out of the ovary, floats down the fallopian tube and then when a sperm gets to it, suddenly it... splits in two or something!? Cause you do realise that the only reason sexual reproduction works is because two HAPLOID cells meet up?
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replied September 22nd, 2007
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Eiri wrote:

Exactly, you are misinformed, or lying, or just plain confused.

The egg cell is HAPLOID from around the time of ovulation all the way until fertilization. What do you think happens!?

What, a 46 chromosome egg pops out of the ovary, floats down the fallopian tube and then when a sperm gets to it, suddenly it... splits in two or something!? Cause you do realise that the only reason sexual reproduction works is because two HAPLOID cells meet up?


That is exactly what I am saying. An egg becomes haploid after fertilization, when meiosis ll is complete.
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replied September 22nd, 2007
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If you are interested, read this exchange on an abortion debate board I think many of you would find interesting:


platero55 wrote:
Chris wrote:
platero55 wrote:
Chris wrote:
If 46 chromosomes makes a human, a human, then sperm and eggs cannot be human as they only contain 23 chromosomes.


This is incorrect - the ovum (egg) has the full 23 *pairs* of chromosomes up until the part of fertilization called "second meiosis". Sperm do not fertilize haploid eggs; they fertilize MII oocytes, (eggs)* which are still diploid.


Uh..no. The egg and sperm which are involved in fertilization are BOTH Haploid cells. Each one has 23 Chromosomes, and its only through fertilization that he diploid number is restored.


Uh..no. You (and Wikipaedia) are working with outdated information. When we get into the details of how sexual reproduction actually works, our conceits regarding what we know tend to get knocked askew. I learned these facts a couple of years ago, and my first reaction was something like "waitaminute, that can't be right". But it *is* right, and I've adjusted my views accordingly. Here's a reference:

Quote:
"When the sperm first makes contact, THE OOCYTE IS STILL DIPLOID, still only halfway through its second meiosis. The oocyte has no nuclear membrane at this stage; the chromosomes are suspended within the cytoplasm, held in position by the spindle. The touch of the sperm on the oocyte's outer membrane stimulates the second meiosis to move to completion. The second polar body is then extruded; the remaining chromosomes acquire a new nuclear membrane and SO FOR THE FIRST TIME FORM A HAPLOID PRONUCLEUS." [emphasis mine] -- from "The Second Creation: Dolly and the Age of Biological Control" by embryologists Ian Wilmut and Keith Campbell


Summing up so far, the ovum is diploid, and remains so until the 2nd meiosis begins. The ovum "loses" 23 chromosomes to accommodate the new genetic material introduced by the fertilizing spermatozoa.

Furthermore, the chromosomes of the sperm and egg do not meet until after the fertilized egg divides:

Quote:
"There is no diploid nucleus, with a complete complement of chromosomes, until we reach the two-cell stage. This biological detail has all kinds of implications. For example, most people tend to assume that a new individual is 'conceived' when sperm and egg meet to create a zygote. But in the zygote the male and female genomes remain separate until the zygote itself divides. Do two divided individuals form 'an individual'?"


Here is a more detailed description of meiosis:

http://users.rcn.com/jkimball.ma.ultranet/ BiologyPages/S/Sexual_Reproduction.html#Oo genesis

And a short quote:

Quote:
In contrast to males, the initial steps in egg production occur prior to birth. Diploid stem cells called oogonia divide by mitosis to produce more oogonia and primary oocytes.


Many of us (including me) have been working with knowledge provided by conventional wisdom and simplified popular science. Only the CW and SPS have turned out to be wrong. Actual biology has a way of confounding our conventional wisdom about How Things Are.
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replied September 22nd, 2007
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Here is another source, this time from a PRO-LIFE author:

Basically it says what I have said. Also, all of the eggs that pass UNFERTILIZED during menstruation are diploid.

In human embryology, "diploid" means the cell contains "46" chromosomes; "haploid" means the cell contains "23" chromosomes. In fact, immature germ line cells (both female and male) are diploid (not haploid) until the last period of their growth and development. Both must pass through two stages of meiosis (meiosis 1 and meiosis 2) before the number of chromosomes in the cell is halved. Spermatogonia are diploid until their last weeks of maturity; and primary oocytes remain diploid until and unless they are fertilized by a sperm (otherwise, they die as diploid).

http://www.lifeissues.net/writers/irv/irv_ 118erroneous101.html
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replied September 22nd, 2007
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futureshock wrote:
Eiri wrote:

Exactly, you are misinformed, or lying, or just plain confused.

The egg cell is HAPLOID from around the time of ovulation all the way until fertilization. What do you think happens!?

What, a 46 chromosome egg pops out of the ovary, floats down the fallopian tube and then when a sperm gets to it, suddenly it... splits in two or something!? Cause you do realise that the only reason sexual reproduction works is because two HAPLOID cells meet up?


That is exactly what I am saying. An egg becomes haploid after fertilization, when meiosis ll is complete.

Noooo!!!!!

An egg becomes DIPLOID after fertilization.

Haploid means HALF. Aka, HALF the chromosomes aka 26.
Diploid means TWO, aka the two halves - 46.

You have biology VERY wrong. Extremely wrong.
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