Take the 2-minute tour ×
Biology Stack Exchange is a question and answer site for biology researchers, academics, and students. It's 100% free, no registration required.

Basically, what I'm asking is, is the actual sperm cell built from the blueprint in the DNA of the man or is it itself also a consequence of the DNA it carries?

I'd like to know a few more things related to this. For example, which DNA is in the nucleus of a sperm? Is it the same as the DNA of other bodily cells in the man's body, or is it just the DNA it's delivering? Can the sperm's performance be affected by any specific genetic traits that can be observed in a potential human the sperm could make? For example, a sperm swims faster if it's carrying the genetic material that would result in a tall person (probably a silly question).

The original question I had is if the statement that female sperm live longer is true. If it turns out that the man's body makes all the sperm more or less the same and they're just boxes that can swim, then I would guess the answer is no.

share|improve this question
    
Does not answer your question but is related: (inter-males) Sperm competition –  Remi.b Apr 14 at 20:28
    
Sperm Biology: An evolutionary perspective might help here - I'll take a look this week at work. There is also a group in my department looking at selection in the haploid/gametic phase so I'll chat to them. –  GriffinEvo Apr 14 at 20:57
add comment

3 Answers 3

I think there is a strong driving force for sperm to be free living haploid versions of human beings. Since they are a product of meiosis sperm are the product of recombination of both the male chromosome sets.

While I'm sure that if we look closely enough, the germline cells that produce the sperm are contributing some protein and structure to the sperm, the life cycle of the sperm is mostly the result of the genome that it contains within itself. Sperm are prone to defects. On the average in human beings about half of sperm are non-motile: simply unable to form the flagellum or power its motion adequately for motility. That's a pretty strong selective force in the life of our other, 'half genome' selves.

Sperm selection - the sorting of which sperm from a single male achieves fertilization is pretty rigorous. It can take 30 minutes to days. Once in contact with the ovum, the sperm executes a critical set of transformations and biochemical activations to get past the various layers of the cell.

Sperm are from the man, but they are each living creatures on their own which we hope will deliver themselves up to the ovum to create another human being. They vary in their genetic quality and effectiveness and this is highly related to their genetic make up.

Because each sperm is the product of two stages of Meiosis, they can be full of genetic defects, most of which would be fatal in a diploid human being. The functions of the sperm as it goes through its short but competitive life weed out genetic abberations and help assure that the next generation of diploid human beings is as healthy as they can.

So they are not DNA boxes that swim. I'd be hard pressed to think of a passive role for a cell in biology - they are all working pretty hard... I'd be interested in a comment with suggestions of something that is not under selective pressure in biology.

It sort of reminds me of the old argument about passive mating in females. Behavioral biologists used to think that female animals had little or no active role in mating. That myth was retired about 30 years ago now. That link points to an introduction to an entire volume reviewing that whole discussion of active female roles in reproduction in case anyone reading is interested.

BTW I'm not an expert on gametes, but I'd be surprised if the ova also didn't have a complimentary but quite different selective process they had to get through to become a fully presented candidate for fertilization.

Just to add a note about how the functioning sperm genes affect the diploid organism: This is one of the most important things that sperm does. The genes that function in the living spermatazoan are the same genes the diploid organism uses, or at least a substantial number of them. Further, these genes are scattered across all the chromosomes and so major chromosomal defects and important genes are functional if fertilization is completed. As an example here's a cool blog post about how mosquito sperm have been shown to use odorant receptors to orient themselves in the fertilziation process. Those same receptors and the signalling genes that link that signal to the sperm behavior are probably quite useful to the adult mosquito. I'd be surprised if human sperm also did not use similar pathways to function.

Not to beat a dead horse, but the recent nature has a report of small RNAs in mouse sperm as being an epigenetic carrier for stress.

share|improve this answer
    
Thanks for the answer. What's still confusing to me is the connection between a sperm not functioning properly and a potential human not functioning properly. For example, humans with mental retardation often have above average strength. Does that mean the sperm they used to be was defected or above average? It seems to me that there would have to be some defined standard of a normal DNA that the sperm would check against to determine how "broken" it is, and I doubt there's something like that. –  Darwin Apr 15 at 7:23
    
Hey Darwin - I've added a note above. you have to remember that a substantial of human genes are found in yeast. Those core functions are absolutely necessary for viability. Our lives as single celled organisms use most of the same genes. neat, eh? –  shigeta Apr 15 at 17:56
1  
Meiotic drive would be a cool example of a sperm cell's genotype affecting it's phenotype –  GriffinEvo Apr 15 at 18:30
    
@GriffinEvo are you thinking of selfishness, sometimes referred to as Drive? If so you have brought up one of the most famous examples of sperm activity - a locus which causes a sperm that contains it to actually inhibit other sperm even if they come from the same male. A classic example of sperm genes in action and evolutionary biology. –  shigeta Apr 15 at 19:35
1  
yes, SD in Drosophila and T-haplotype in mice are the two main examples if i remember correctly –  GriffinEvo Apr 15 at 22:11
show 2 more comments

Shigeta, you have some good points there. I wanted to clarify some things.

Sperm and ova are considered tissues, not individual living creatures. They are not individually capable of cell division nor production of offspring. They are specialized cells with specific functions that are created by a multicellular organism as a means of transferring DNA.

The sperm carries 1/2 of a chromosome set from the male's own DNA, after cross-overs during meiosis (meaning that the DNA in a sperm has some different combinations than the parent DNA).

Metabolism primarily occurs at the mitochondria. Protein synthesis does occur in the sperm, using nucleus-encoded mRNA. What I was unable to find an answer to was whether this mRNA was transcribed from the nucleus of that same sperm, or whether it was from the primary spermatocyte DNA (diploid) or from the sperm nucleus (haploid). The chromatin in the sperm nucleus is several times more tightly wound than in a somatic cell, so I am not sure how it would be accessible to transcription, nor am I sure that the full set of enzymes required for transcription, modification, and translation is present in the spermatozoa. I'll be very interested in hearing if anyone is able to find this information!

share|improve this answer
    
what does a sperm do besides reproduce? The haploid phase of some animals like coral can be weeks long. Yeast haploid genetics are a big topic in research and the halpoid phase can be maintained for quite a while. Here's a reference for sperm mitochrodrial transcription. Sperm are not the main system for research of hapoid life cycle though humrep.oxfordjournals.org/content/22/6/1585.short –  shigeta Apr 15 at 14:06
    
I really don't know who makes these decisions, but I'm not sure this is an unanimous opinion nor one that is necessary to hold in all circumstances. you are of course free to have whatever opinion you like. –  shigeta Apr 15 at 17:58
add comment

For example, a sperm swims faster if it's carrying the genetic material that would result in a tall person

and in the comments

It seems to me that there would have to be some defined standard of a normal DNA that the sperm would check against to determine how "broken" it is, and I doubt there's something like that

If some aspects of sperm cells indirectly connected with some parts of phenotype, so we can expect that result, but not because of sperm cell carries that noble phenotype gene.

DNA in sperm cell is packed and not expressing (not transcribed).
Because DNA is packed and because test checks consuming energy, which sperm needs for another tasks - pretty wise to shut down checks, repairs.
Also DNA is not like ZIP archive, where cell can check the check sum, to make shure it works witch good DNA. Cell have difficulties working with information, if it needs to connect information results from distance sources. (Let say as example: if gene A have mutation A* and gene B have mutation B* then do X).

Also there is big big difficulties with that mater: some defined standard of a normal DNA - all DNA that leads to organism which is able to procreate, to survive - is good enough for nature. Thats Evolution spirit). And who can, who not - will be sorted out, later and with 100% accuracy.

For example, humans with mental retardation often have above average strength.

Our DNA actually consists from imperfections, which showed up long ago and became standard de facto, some are compensated at the moment and are RFC(Request for Comments). This or another set of genes is a balanced system. Balance can be shifted and that will have some consequences, actually thats how another system is prepared for testing by Evolution factors. By shifting balance far enough, for making some things at extreme, we may expect that another things have to break. But strength is not because of mental retardation, or vice verse. (It may be connected, may be not; also I would not trow away, some ontogenesis matter in that case) They both are results, not cause. But there are some reasons to be connected, if you take look on apes behavior as example.

just boxes that can swim

Man it's a Rocket

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.