Dory's Biology Questions Thread

[Dory]

If a gamete of an organism is fused with a body cell of the same organism, to produce a triploid zygote, why would the resulting organism be sterile?

[GenesForLife]

I'm guessing meiotic failure because pairing of homologous chromosomes doesn't take place.

[Dory]

I'm guessing meiotic failure because pairing of homologous chromosomes doesn't take place.

This question is confusing me on many levels. I saw it on Yahoo Answers. I didn't even know that there are triploid zygotes can exist. So if they exist, apparently they're sterile...because of what meiotic failure? Don't you mean meiosis failure?

[hackenslash]

Great thread. Some really good stuff there, especially from GFL.

[GenesForLife]

I'm guessing meiotic failure because pairing of homologous chromosomes doesn't take place.

This question is confusing me on many levels. I saw it on Yahoo Answers. I didn't even know that there are triploid zygotes can exist. So if they exist, apparently they're sterile...because of what meiotic failure? Don't you mean meiosis failure?

Things related to meiosis are described as meiotic, ditto with mitosis and mitotic, triploid zygotes are regularly used to make seedless fruits, Dory.

Of course, there have been recorded instances of Human triploid zygotes



http://www.advancedfertility.com/triploid.htm


A whole list of literature on the topic can be found here http://scholar.google.co.in/scholar?hl= ... a=N&tab=ws

[Dory]

Of course, there have been recorded instances of Human triploid zygotes

Just zygotes right? Not developed humans?

[GenesForLife]

Of course, there have been recorded instances of Human triploid zygotes

Just zygotes right? Not developed humans?

I don't know about any developed triploid humans.

[Feck]

Of course, there have been recorded instances of Human triploid zygotes

Just zygotes right? Not developed humans?

I don't know about any developed triploid humans.

Not likely look at an extra copy of just a sex chromosome cf Klinefelters

[GenesForLife]

But this is interesting indeed

The karyotype 46,XX/69,XXY was found in a 13-year-old, mentally subnormal patient with club feet, strabismus, eunuchoid habitus, small penis, midscrotal urethrovaginal opening, small descended left testis, and small undescended right testis; no ovarian tissue could be found at laparotomy. Triploid:diploid cell ratios were 60:40 and 4:96 in skin fibroblasts and circulating lymphocytes, respectively. In the triploid line, two of the no. 13 chromosomes had unusually large satellites and one of the no. 22 chromosomes had a brightly fluorescent zone on its short arms. The patient's father was heterozygous for both these autosomal markers; the mother carried neither marker. This, together with the single Y, indicated that the extra haploid set was derived from the father. Of several possible mechanisms, we favor the suggestion that double fertilization occurred; one sperm nucleus immediately fused with the egg nucleus producing the diploid line; the second sperm nucleus was incorporated later into one of the two cells resulting from the first division of the zygote, producing the triploid line.

Triploid cells AND diploid cells both present in a 13 year old human, but not triploid alone.

http://onlinelibrary.wiley.com/doi/10.1 ... x/abstract

But I did find this about triploidy alone, and quote the relevant section(s) of the abstract here

http://pediatrics.aappublications.org/c ... ct/68/1/23

Triploidy results in a clinically recognizable lethal syndrome with hydatidiform placental changes, severe intrauterine growth deficiency, dysplastic cranial bones, eye defects, cleft lip and/or palate, malformed ears, micrognathia, syndactyly, genital anomalies and, rarely, spina bifida.

The google scholar description of the link to this abstract here http://jmg.bmj.com/content/43/7/609.abstract said

Triploidy is a common occurrence in human gestation, present in 2–3% of pregnancies. It often culminates in early spontaneous abortion but occasionally ...

If you are interested in getting the paper you may want to sign up for the BMJ's 30-day free trial

[mistermack]

I'm guessing meiotic failure because pairing of homologous chromosomes doesn't take place.

This question is confusing me on many levels. I saw it on Yahoo Answers. I didn't even know that there are triploid zygotes can exist. So if they exist, apparently they're sterile...because of what meiotic failure? Don't you mean meiosis failure?

At the risk of sounding VERY pompous, there is an important thing to learn in this. "Why are they sterile" is very much the wrong question.
We should be AMAZED if they were fertile.
It's very tempting to picture life as having a purpose. That's how our human minds work. When we are little, we think water is for us to drink, or have a bath. Air is so we can breathe. etc. etc.

But the truth is there is hardly any purpose in anything.
We imagine that creatures exist so that they can reproduce. That's just as wrong. They exist because their ancestors DID reproduce.

Imagine life as a row of dominoes standing on their ends. You knock the first one over, they fall in turn all the way to the end. If the last one gets knocked over, one or two new rows automatically pop up, and it all starts again.
When we humans set dominoes up, we have a purpose, and can fix it if one domino is slightly askew.

Nature has no purpose at all. If one domino misses the next, the end domino never falls, and that line of dominos becomes extinct.
That's your triploid zygote. It never had a purpose. It rarely knocks over the last domino, if even one of them is slightly offcentre.
.

[Feck]

The problem with triploid cells would be mitosis, anaphase and metaphase would be all messed up .

[GenesForLife]

The problem with triploid cells would be mitosis, anaphase and metaphase would be all messed up .

<nods>

[Dory]

I'm guessing meiotic failure because pairing of homologous chromosomes doesn't take place.

This question is confusing me on many levels. I saw it on Yahoo Answers. I didn't even know that there are triploid zygotes can exist. So if they exist, apparently they're sterile...because of what meiotic failure? Don't you mean meiosis failure?

At the risk of sounding VERY pompous, there is an important thing to learn in this. "Why are they sterile" is very much the wrong question.
We should be AMAZED if they were fertile.
It's very tempting to picture life as having a purpose. That's how our human minds work. When we are little, we think water is for us to drink, or have a bath. Air is so we can breathe. etc. etc.

But the truth is there is hardly any purpose in anything.
We imagine that creatures exist so that they can reproduce. That's just as wrong. They exist because their ancestors DID reproduce.

Imagine life as a row of dominoes standing on their ends. You knock the first one over, they fall in turn all the way to the end. If the last one gets knocked over, one or two new rows automatically pop up, and it all starts again.
When we humans set dominoes up, we have a purpose, and can fix it if one domino is slightly askew.

Nature has no purpose at all. If one domino misses the next, the end domino never falls, and that line of dominos becomes extinct.
That's your triploid zygote. It never had a purpose. It rarely knocks over the last domino, if even one of them is slightly offcentre.
.

For the record though I was the quoting the question from another source, it just made me wonder.

[mistermack]

For the record though I was the quoting the question from another source, it just made me wonder.

Yeh, that's why I wrote "at the risk of sounding pompous".
But it's such an easy thing to fall back into, assuming purpose, that you very often come across very qualified people doing it. Especially in evolution, more so than the mechanics of biology. They say, why don't animals evolve this way, or that? which can lead to all sorts of false assumptions.
.

[Feck]

For the record though I was the quoting the question from another source, it just made me wonder.

Yeh, that's why I wrote "at the risk of sounding pompous".
But it's such an easy thing to fall back into, assuming purpose, that you very often come across very qualified people doing it. Especially in evolution, more so than the mechanics of biology. They say, why don't animals evolve this way, or that? which can lead to all sorts of false assumptions.
.

That's true I've heard people talking about anatomy saying that such and such a structure is designed for this purpose