From my layman’s understanding of the conception process, a mix of chromosomes are taken from both parent’s sets and then combined, so within the testes or ovaries would it be possible to extract your parent’s DNA?
Your DNA is a 50=50 mixture of your parents. So in principle you could extract (roughly excluding different size of X and Y chromosome and mitochondrial DNA) half of each parents DNA from you. The other half is not in you at all. I don’t know if there’s any way to tell which was which (except again the Y chromosome and the mitochondrial) without comparing to your parents. And of course a lot of it (basic human structure) might be identical.
I would think that from any cell my body it would be possible to extract the DNA sequences that my father contributed to my own DNA. Finding out which parts of my DNA had come from Dad versus Mom would be nearly impossible without doing genetic tests on at least one parent as well.
Neither would it be possible, from the cells in my body, to work out the entirety of my father’s DNA. Only half of that was in the sperm cell that conceived me, thus the other half is really not part of my biology, and you cannot find out those genes from me.
Does that help?
On preview: OldGuy said it just about as well.
One form of DNA that it is possible to extract fully is mitochondrial DNA.
Mitochondria are sort of a symbiote that dwells within your cells and are vital to respiration. The thing is, despite being a more or less inherent part of your physiology they are essentially a separate creature, with their own DNA. Being separate creatures (which reproduce via binary fission) you have to inherit (quite literally) them from your parents. More specifically you get them from your mother (as they’re present in the egg cells).
As a result you can be said to have (regardless of your sex) your mother’s mitochondrial DNA. Although, as mentioned, you only have half your parents’ actual DNA.
What they said – each parent has two copies of each gene; they give you one of them, so you also have two. You don’t have the other half.
–Cliffy
And before someone asks, it’s not even possible to do a full reconstruction of both parents even if they’re identical twins. Because of the 50/50 mixing, each identical parent might have an A and a B version of a gene, and yet the child could receive both A or both B versions.
What you can’t do is figure out what your father or mother is made of. What you can do, however, is figure out where you got your green eyes or brown hair, or whatever. When you do a RFLP of some DNA, it breaks into some dark and light bands. If you have a dark spot in a certain place, your father does too, and your mother doesn’t, you can say with full confidence that that gene came from your dad.
You can’t tell, however, what gene is making that dark spot is. If you tossed in your whole genome, it could be any part of you. If you threw in only, say, the tail of chromosome 17, then you could narrow it down.
In other words, you can’t tell what you parents have, but you can tell who gave you what you have.
As I understand it ( not a biologist ) that’s not true, actually. A fair amount of DNA is “myelinated”; attached to a protein that shuts it down, according to which parent it comes from. Your mother’s and father’s genes are unevenly responsible for different parts of the body; for example the father’s and mother’s genes are in charge of growing different parts of the brain; you inherit the genes for that area of the brain from both parents, but the genes of one are inactive in areas of the brain where the other is active. In fact, this was one of the biggest problems with cloning mammals; the myelination kept DNA from body cells working properly in reproductive cells; the breakthrough in cloning mammals came with methods of removing the myelination.
So at least some of your DNA is essentially labeled according to which parent it came from.
The term you’re probably thinking of is “methylation” and refers to methyl groups, not proteins, attached to DNA, but otherwise you’re right about this. The process is known as genetic imprinting, and it’s pretty important for silencing or lowering the dosage of certain sex-specific genes.
This can lead to some odd scenarios where losing a chunk of the same chromosome will cause two completely different disorders–Prader Willi Syndrome orAngelman Syndrome–depending on which parent’s chromosome was damaged. This is because the undamaged maternal chromosome has certain necessary genes permanently turned off, so it can’t compensate for the loss of the paternal genes, and vice versa.
:smack: Bah, you’re right.
Having parents that are identical twins is not a realistic scenario - Identical twins always have the same sex.
I can’t believe it … no-one’s made a joke yet. (I’ll keep it to myself)
Are we excluding the Y chromosome here, which must come from the father?
Yes, there are a few exceptions, including the Y chromosome, the X chromosome (if you’re male), the mitochondrial DNA, and methylated areas. But generally speaking, for the most part, you won’t be able to tell which stretches of your DNA come from your father and which from your mother.
Additionally, just to throw this out, because of crossover events, your chromosomes won’t look like your parental chromosomes. For example, your chromosome 1 that you got from your father will be a mixture of his two chromosome 1s - part from his maternal chromosome and part from his paternal chromosome. It’s all his genetic material, just rearranged.
I’ve often wondered how often this happens. In a given individual’s genetic material, how many crossovers should one expect to have occurred from the previous generation?
Every chromosome undergoes multiple crossover events during meiosis. In fact, there’s some evidence that crossovers are necessary for faithful chromosome segregation. I don’t recall offhand the average distance between crossovers, but it’s in either kilobases or megabases.