[Daisy]

Are there genetic differences in the eggs that a woman produces. What I mean is that a woman can produce hundreds of eggs in a lifetime. Are each of these eggs genetically dif from each other. The same question applies to sperm. Is each sperm a man produces genetically diff from all the others? I ask this question because I am trying to understand how children with the same parents are not genetically the same. They are similar but they don't look the same nor do the necessarily have the same skills or abilities. Is it because the eggs and sperm themselves are slightly different?

[Tormod]

Well...your question is the answer. Since not every child of the same parents are the same, the eggs and sperm must be different.

How children turn out is based on heredity, which means that we inherit certain traits from our parents. Each egg and each sperm are not only different, but they also respond differently to temperature, stress, time of day and so on. So the entire process from the creation of the egg/sperm cells to the conception plays a part in which traits will be passed on to the child.

Here's a page:
Genetics

Tormod

[Daisy]

Tomond,

Thank you for the site on heredity. It is very informative but it does not explain how a person's heredity seems to depend largely on the order in which they were born and the sex of the first child (and first pregnancy) in a family. What I have observed both in my own family and in many others is that if the first child (and first pregancy) is a girl, she will look more like her father than her mother. The next child to be born, regardless of sex, will resemble the mother. If there is a third child, that child (again regardless of sex) will look like the father (and so on). If the first child in a family is a boy, he will look more like the mother and the second child (regardless of sex) will look more like the father.

I just don't understand how that happends.

[phoenix]

Daisy,

It would be interesting to quantify your observation. I have no explanation for it, neither can I confirm it specifically. I could take a rough guess that because the first child born in a relationship is more likely to be a biological child of the father, it would benefit that child to look like him. Subsequent children are more likely to be the result of extramarital affairs.

I have noticed that children do not resemble anyone specifically when they are young. Indeed, it has been suggested in the scientific literature that children for the good of their genes should lay off exposing any similarities with their fathers, since they may not be raised by their biological father, and, well, he might be crossed when he figures and kill the child.

What I have also noticed is that children whose paternity is debated tend to look like their fathers sooner than others (e.g. Boris Becker, Bill Clinton, Mick Jagger). That makes evolutionary sense.

NB: I am writing in GENERAL TERMS, not specifically about humans, so please hold back your flames!

Regards,

Phoenix

[Tormod]

Well, in my experience both my daughters look like me - and they have done so since they were born!

Tormod

[bugmenot]

If a females eggs differ in genetic quality how are the eggs selected to be released?
For example in males the weak sperm die off before making it into the egg. Is there such a process in females? Are eggs released randomly or are they selected by something for the best possible quality?
I believe that some eggs are bad and that they get released randomly. If that is true are female eggs responsible for weak genetics more than a males sperm?

[Fishteacher73]

The viablity of the sperm has nothing to do with the rest of the genetic material held there in, so the culling of "slow swimmers" has little to do with the over all genetic fittness of the spem (although it will remove individuals with massivly malformed geteic stucture, such as very poorly divided sperm, etc).

[EWright]

Uhg, female Tormods, dying sperm and patterns of similarities in random propagation...

It's not that the weaker sperm die, it's that the stronger swimmers get there faster. Even then, it is not a first come first serve basis. The sperm carry a chemical on their tip that breaks down a barrier, so many of them are needed for one to penetrate the egg. If just one sperm gets there, as they might tell you in school, you're not likely to become pregnant. However, it's likely that if one gets there, he has a bunch of homies with him .

There may be similarities in patterns you've observed in your family and others, dependant on what sex child was born first. However, the process is entirely random. Any similarities you observe, are coincidence. Choose a larger group to study and make sure you're not reading into it. It's random because each sperm and each egg are formed uniquely through a process called meiosis. The observed similarities between parents are because the genes inhereted by each sperm or egg are replicas of each parent. Each has half of the DNA of each parent's normal cells. So when you combine them, you get the total number of 23 pair of chromosomes that all healthy humans have.

Also, the sex of the child is fully dependant on the father and has nothing to do with the mother's egg. This is because the mother only produced the X chromosome, while the father produces both X and Y chromosome sperm. Therefore, his Y chromosomes are needed to produce a son (XY combination).... whereas his X, if it reaches the egg, will produce a daughter (XX combo).