Thread: DNA

Just a quick question.. Does anyone have a site with proof on it that states that DNA is not hardwired and that it is a recent discovery?

DNA is a molecule.

It is not a recent discovery, people have been working with DNA since the late 1800's; a complete understanding of it's structure was discovered in the 1950's. The wikipedia article on DNA has a nice summary.

But I don't know what you mean by hardwired in this case. Usually when people use that term in biology they're referring to a trait being hardwired in the DNA.

Well, a friend and I were talking.. My friend is an english teacher and is fairly educated. I am going to school to hopefully get a degree in genetics.. He says that DNA can't be changed and RNA can be changed. I informed him that biologists use to think that way, but they have recently figured out that DNA isn't set in stone after something is created. It can be altered after the specimen has been created.

DNA can be changed. Evolution couldn't happen otherwise.

Something around the time of 1835 suggested it but it wasn't until later one that it was demonstrated, probably like early 1900's.

Just look up DNA mutation.

DNA can even be changed in a developing organism. Transposons are segments of DNA that "jump" around the genome, and retrotransposons copy themselves, then put the copy in other parts of the genome. B lymphocytes rearrange their DNA to make different antibodies. And then there are viruses, some of which incorporate their DNA into the host cell's genome.

Somatic hypermutation in B cells is another example of DNA changing within the organism.

Edit: Assuming the previous poster was talking about the diversity generating factors involved in the VDJ splicing during lymphocyte maturation.

Part of my post was, yes.

I heard that a woman's DNA varies more, throughout her life. Anybody know about that?

It will be important to know what you mean by "hardwired."

There are Epigenetic mechanisms, where certain traits are controlled by the modification of DNA by processes such as methylation. This sort of modification is not necessarily encoded in the DNA sequence itself, but rather affects the structure of the chromosome and its translation into RNA.

Many people mistakenly confuse epigenetics as the affects that the environment has on translation. That, however, is incorrect. Environmental factors can result in epigenetic changes, but not all epigenetic changes are environmental. Additionally, the original understanding of epigenetics included inheritance in the next generation.

Originally Posted by Pong

I heard that a woman's DNA varies more, throughout her life. Anybody know about that?

In what respect? They don't undergo somatic or germ line mutations at a different rate to any other humans, as far as I know. The hyper mutations their lymphocytes undergo are the same too.

Originally Posted by TheBiologista

Originally Posted by Pong

I heard that a woman's DNA varies more, throughout her life. Anybody know about that?

In what respect? They don't undergo somatic or germ line mutations at a different rate to any other humans, as far as I know. The hyper mutations their lymphocytes undergo are the same too.

I guess there's nothing to it.

Originally Posted by Pong

Originally Posted by TheBiologista

Originally Posted by Pong

I heard that a woman's DNA varies more, throughout her life. Anybody know about that?

In what respect? They don't undergo somatic or germ line mutations at a different rate to any other humans, as far as I know. The hyper mutations their lymphocytes undergo are the same too.

I guess there's nothing to it.

Perhaps it was something to do with micro chimaerism? Women who conceive seem to retain a small population of cells from their children after they give birth. The cells seem to behave rather like mesenchymal stem cells. Function, if any, is not all that clear. So a woman who has had say, three kids, will have detectable DNA from 4 individuals, if we sample enough cells.

perhaps he's referring to mutations in the ovum which increases with age?

Originally Posted by Robbie

perhaps he's referring to mutations in the ovum which increases with age?

Ah, I think we have a winner. Nice one Robbie.

Originally Posted by TheBiologista

Originally Posted by Pong

I heard that a woman's DNA varies more, throughout her life. Anybody know about that?

In what respect? They don't undergo somatic or germ line mutations at a different rate to any other humans, as far as I know. The hyper mutations their lymphocytes undergo are the same too.

Don't men's high rate of sperm production over a lifetime make them more likely to develop potentially cancerous mutations?

It makes male sperm prone to generate wonderful novel adaptative mutations!

HOORAH for male sperm!.

Originally Posted by gottspieler

Originally Posted by TheBiologista

Originally Posted by Pong

I heard that a woman's DNA varies more, throughout her life. Anybody know about that?

In what respect? They don't undergo somatic or germ line mutations at a different rate to any other humans, as far as I know. The hyper mutations their lymphocytes undergo are the same too.

Don't men's high rate of sperm production over a lifetime make them more likely to develop potentially cancerous mutations?

Can't say I've ever heard that. Source?

Originally Posted by TheBiologista

Originally Posted by gottspieler

Originally Posted by TheBiologista

Originally Posted by Pong

I heard that a woman's DNA varies more, throughout her life. Anybody know about that?

In what respect? They don't undergo somatic or germ line mutations at a different rate to any other humans, as far as I know. The hyper mutations their lymphocytes undergo are the same too.

Don't men's high rate of sperm production over a lifetime make them more likely to develop potentially cancerous mutations?

Can't say I've ever heard that. Source?

The reason I asked was that I remember reading it but forget the source...it may have been the Sci Am special cancer edition or a Bio text...I honestly don't recall...

I wasn't really thinking about reproduction, but this is interesting...

Originally Posted by Robbie

mutations in the ovum which increases with age?

Originally Posted by gottspieler

Don't men's high rate of sperm production over a lifetime make them more likely to develop potentially cancerous mutations

So, which mutates quicker?

And, could we reproduce with, say, banked cord blood?

If I remember correctly, men simply make more gametes than women do, so the chances are higher that a sperm containing a mutation will be involved in fertilization. In gametogenesis for men, one spermatocyte goes through meiosis to become four sperm - 4 chances for mistakes to happen. For women, however, the oocyte goes through meiosis but only one of the 4 resulting daughter cells becomes an egg; that's because the majority of the mother cell's cytoplasm goes to the one egg, leaving the other three tiny and unfit to be eggs - so, in essence, one chance for mistakes to happen. But for both sexes, the machinery of mutation repair seems to lose effectiveness with age, so in that sense mutation rates increase at relatively equal rates for men and women, from what I understand.

In theory we could reproduce with cord blood, once we learn how to properly differentiate stem cells into gametes. I don't know what the current state of research is in that area.

Originally Posted by paralith

If I remember correctly, men simply make more gametes

It's been a long time huh?

Originally Posted by paralith

only one of the 4 resulting daughter cells becomes an egg

Cool. Thanks.

I'm confused now. So these eggs refresh themselves, even at the same rate male gametes do? The way I hear it (maybe dumbed-down) is that the egg of a 50-year-old woman really is a 50-year-old egg.

The period of renewal would reflect an optimal strategy for genetic integrity, I imagine. So, knowing this, we could predict the relative mutation hazard of division vs. longevity.

Originally Posted by Pong

I'm confused now. So these eggs refresh themselves, even at the same rate male gametes do? The way I hear it (maybe dumbed-down) is that the egg of a 50-year-old woman really is a 50-year-old egg.

The oocytes are formed shortly after birth, and no more are made during life. But when it is time to ovulate an oocyte goes through meiosis to form a mature egg. However, even living oocytes are vulnerable to mutation, and need to be maintained for all those years.

Originally Posted by paralith

The oocytes are formed shortly after birth, and no more are made during life.

Right, but do each regenerate through ongoing (single-daughter) mitosis throughout a woman's life? Or does each cell exist for years in stasis?

Originally Posted by paralith

But for both sexes, the machinery of mutation repair seems to lose effectiveness with age, so in that sense mutation rates increase at relatively equal rates for men and women, from what I understand.

Don't know if this is pertinent, but in all the works I've read, the fact is that the sperms are produced in male testes as generations after generations, with cell division constantly going on. So a 40 year old male will be producing sperm that many generations (in terms of the cells producing it) older than that of a 20 year old male. Hence the far higher rate of mutation and non-motile sperm in older men.

In women, as you point out, each egg is exactly the same cell (more or less) as the one she was born with.

As for the OP, this may again be a predicate logic problem. Is the English Literature feller talking about an individual molecule of DNA or the DNA structure of a particular person in general, or about the qualities of DNA molecules as a class?

If an individual DNA molecule is subject to change then it is quite simply no longer the same molecule.

If it is the DNA of person we are speaking of, then every cell division will produce some mutations so that (I believe) technically speaking, no two cells will have absolutely identical DNA.

If we are talking about DNA as a class, then there is some hope of a realistic answer, and it would be along these lines:

1. All the RNA in a person will tend to be produced using a DNA template (or an RNA template itself taken from the DNA). In that case, all our RNA is custom-built based upon the 'hardwired' DNA.

2. If that is the way in which the Literateur was referring to it then he is absolutely right, but this difference is of little consequence or moment. We create RNA to suit our needs, based upon the DNA template.

3. Some viruses, on the other hand, use RNA as their template, so for them it is RNA that is 'hardwired'.

Dunno if this helps, but them's my thinks. (And it's a day after New Yea and I'm awfully hungover and weary...)