Twins or not?

  • Thread starter pivoxa15
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Answer to question in OP

  • Yes

    Votes: 1 7.7%
  • No

    Votes: 12 92.3%

  • Total voters
    13
  • #26
Moonbear
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Note that even identical twins often look a bit different, especially as they get older. That's because some of our appearance is not due to purely genetic factors, but some environmental factors, i.e., how much weight we gain, sun exposure (I have cousins who are identical twins and look very little alike as adults...one loved going out in the sun as a teen, and the other pretty much stayed indoors, so one has a lot of sun damage, wrinkles, freckles, and the other doesn't), and even hairstyle can make you look pretty different.
 
  • #27
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Note that even identical twins often look a bit different, especially as they get older. That's because some of our appearance is not due to purely genetic factors, but some environmental factors, i.e., how much weight we gain, sun exposure (I have cousins who are identical twins and look very little alike as adults...one loved going out in the sun as a teen, and the other pretty much stayed indoors, so one has a lot of sun damage, wrinkles, freckles, and the other doesn't), and even hairstyle can make you look pretty different.
Fair point.
 
  • #28
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The eggs that the mother produces have different combinations of genes from the mother--each egg has a different set of genes. Likewise The sperms that the father produces have different combinations of genes from the father. So when one egg and one sperm unite, they make a unique individual that is NOT an exact copy of either the mother or father.

Usually just one egg is released from an ovary. After it is fertilized by a sperm it begins to divide into more and more cells and grows into a baby.

Sometimes, though, more than one egg is released and each gets fertilized by a different sperm. These grow into twins which are not identical. Since each baby grew from a separate egg+sperm combination, they are no more similar than their other brothers or sisters born years earlier or later.
Still, eggs produced within a period of time can be different to eggs produced at a later time. Same as sperms. So non identical twins can still be more similar than to siblings born years apart? Say 10 years would be a noticable difference.

This raises the question: Is it true that the sperm and egg 'quality' decline as one ages? Although someone define quality as I don't know how to. If so when is the peak times for male's sperm and female's egg?




However, sometimes AFTER a single egg+sperm are combined, when the cells start to divide to make a baby, some of those early cells don't stick together well and break away. Now you have two or more clumps of cells that came from the SAME egg+sperm! So the babies that grow from each clump are identical.
That would be much more rare? How rarer compared to non identical twins?
 
  • #29
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Still, eggs produced within a period of time can be different to eggs produced at a later time. Same as sperms. So non identical twins can still be more similar than to siblings born years apart? Say 10 years would be a noticable difference.

This raises the question: Is it true that the sperm and egg 'quality' decline as one ages? Although someone define quality as I don't know how to. If so when is the peak times for male's sperm and female's egg?
You're exactly right about egg and sperm quality being related to age of the parents. My guess is that the ideal time physically is probably between age 17 and 34. There's the mother's ability to carry the baby safely, of course, and most damage to genes occur as a mother approaches mid 40s. Father's sperm health also declines, but more gradually--that's why we still sometimes hear about 80-year-old fathers. I did recently read about certain types of defects actually being more common with very young mothers, but now I can't remember the details.

Of course, the differences in children that are related to age of parents isn't really a matter of benign forms of similarity or differences like hair color, build, and so on. Those difference are caused strictly by which of the mother's genes happened to end up in the egg that was used and which of the father's genes happened to end up in the sperm that was used. Those things are not related to age of the parent. The age of the parents affects only the probability of birth defects and gestational health of mother and baby.

For eggs, they are all created when the the mother is in HER mother's womb. For sperm, they are created within months of being used (older ones just die). The mother's eggs degrade over time and the father's specialty cells that produce sperm also degrade over time. Also various toxins collect in everyone's body over the years (like xenoestrogens) which damage the reproductive efficiency and reliability, cause birth defects and bad fetal health, and also cause many other common life-threatening problems in the adults, or in a baby when it grows up. So the only difference in later-born children really has strictly to do with the probability of birth defects rather than how similar they look to siblings near their age.

On a side note, this gives me a chance to propound that the xenoestrogen problem is really bad and people need to take notice. The ill effects of xenoestrogens don't show up for years, sometimes decades--so we are only now noticing it. Xenoestrogens don't biodegrade much at all, and they collect in fatty tissues (so they build up in the food chain). Studies over the last couple decades are now proving that they are the cause of a myriad of life-threatening problems. They are the cause of the 50% drop in men's sperm counts of the last few decades, damage to sexual development in children, and they are the cause of most breast, prostate, and ovarian cancers that occur! Xenoestrogens come from herbicides, insecticides, cosmetics, plastics food containers, certain common solvents and emulsifiers, synthetic clothing (through the skin and when the lint is inhaled) and other places.

That would be much more rare? How rarer compared to non identical twins?
Looks like the probability of having identical twins is about 1 in 280, fraternal twins 1 in 125.
 
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  • #30
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Birth defects being the genes not properly transcribed and carried out?

When that happens at a minor level, the effects will show later in the baby's life?

What do you mean by degrade of sperm and egg?

fraternal twins being twins with different fathers?
 
  • #31
jim mcnamara
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fraternal twins are dizygotic twins - twins formed from two separate eggs combined with two separate sperm. Creates two individuals. Not necessarily the same sex and definitely not with the same genes.

identical twins are monozygotic - formed from a single egg combined with a signle sperm.
The zygote divides forming another identical zygote. Each one (total of 2) goes on to form a separate individual. You get 2 people of the same sex with identical genes.

-- just to clarify. You guys are throwing terms around and it is confusing to other readers.
 
  • #32
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Birth defects being the genes not properly transcribed and carried out?

When that happens at a minor level, the effects will show later in the baby's life?

What do you mean by degrade of sperm and egg?

fraternal twins being twins with different fathers?
"Birth defects" simply means any wrong development in the baby, whether caused by genetic damage, trauma (injury), or chemicals.

By "degrade" I mean genetic damage or possibly weak sperm (that can't swim well).

Fraternal twins mean twins that aren't identical.

The older the parent, the more likely the genes in the egg or sperm will be damaged (because cells have had longer to get damaged), and thus the less likely a fetus will be viable and if it does grow the more likely it will have genetic defects. Its a higher probability but still fairly low. Down syndrome is the classic example--the probability increases substantially as a mother gets into her 40's, but even then its something like 1/600 if memory serves me. Typically genetic damage is apparent early on--its affects aren't necessarily that delayed or hidden.

Xenoestrogens typically won't cause genetic damage in a fetus, however they can cause genetic damage in that fetus's offspring (by messing up the fetus's ability to create good sperm or eggs)! Xenoestrogens alter the development of the baby just like too much estrogen would. They collect in people and so are more dense in older people. Xenoestrogens cause feminization of male babies, damage to the fetu's ability to create sperm or eggs, early puberty in girls, and other things. They also pretty much explain why men's sperm counts have dropped so profoundly in the last few decades. Xenoestrognes in adults are the prime cause of some common cancers and other things.

Here's a good starting point to see all the studies that have been done that clearly show these things are happening. Also you'll see how doctors often treat patients with xenoestrogens thinking they will help certain problems when they simply exacerbate them (like menopausal symptoms). (Note that the pharmaceutical companies only push non-natural substances because they aren't allowed to patent natural substances, and that pharmaceutical salesmen are often the only source of information a doctor has because doctors are too busy to read the journals propounding the studies!)

Here's the link:
http://www.johnleemd.com/store/resource_references1.html

.
 
  • #33
It takes some time for ovulations to resume after one gives birth, though that time varies among individuals and whether or not one is breast feeding. But, still possible to have a baby born in January and another in December (especially if the second is a bit premature).
Even if it's the normal way that a woman recovers from childbirth this isn't always the case. I have two cousins who are roughly nine months apart. I don't remember their birthdays exactly but I know it's nine months & a week or two. Lol, the doctor told my uncle to let the stitches heal next time. Anyway, to answer pivoxa15's original question no, two babies born in the same year don't have to be twins.

Still, eggs produced within a period of time can be different to eggs produced at a later time. Same as sperms.
Actually women are born with all the eggs they will ever have, not 100% sure of the number but I think it's in the neighborhood of 40,000 eggs.
 

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