Spermatogenesis Question

[justadream]

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Replication of DNA precedes Meiosis. I get that. But for sperm production, in which stage (spermatogonium or primary spermatocyte) does this replication of DNA occur?



I guess my second question is: what is the difference between a spermatogonium and a primary spermatocyte?



I know that the spermatogonium undergoes mitosis to create primary spermatocytes. But what is the “line” that must be crossed so that a particular spermatogonium can progress to the other stages? Is it simply that each spermatogonium only undergoes mitosis once?

 

[sillyjoe]

This schematic should be helpful. It helps to understand that this terminology was developed mainly by histologists who viewed these cells under microscopes and gave them names based on the way they stained/looked and their genetic features. Follow the flow chart and match it up to the histological presentation to get a clearer picture of how the sperm develops in the seminiferous tubules.

2n: diploid
n: haploid

 

[justadream]

@sillyjoe

I actually thought of this question while staring at a very similar diagram lol.

If you see, the spermatogonium does mitosis to make another spermatogonium. But when does this mitosis end (so that the spermatogonium can progress to the other stages)? Do I just assume each spermatogonium only does mitosis once before progressing on?

 

[sillyjoe]

@sillyjoe

I actually thought of this question while staring at a very similar diagram lol.

If you see, the spermatogonium does mitosis to make another spermatogonium. But when does this mitosis end (so that the spermatogonium can progress to the other stages)? Do I just assume each spermatogonium only does mitosis once before progressing on?

I really am having a hard time understanding your question. Can you rephrase it? By having these mitotic divisions, it increases the amount of spermatocytes made from a single germ cell. That is really all I think you need to know aside from the fact that primary --> secondary is diploid --> haploid and that it occurs in the seminiferous tubules.

 

[justadream]

@sillyjoe

Okay so you have a spermatogonium which can do mitosis to make another spermatogonium.

Theoretically, this process could go on forever (making infinity spermatogonium).

At what point does any one spermatogonium decide "enough is enough" and being the process to become a primary spermatocyte?

 

[sillyjoe]

@sillyjoe

Okay so you have a spermatogonium which can do mitosis to make another spermatogonium.

Theoretically, this process could go on forever (making infinity spermatogonium).

At what point does any one spermatogonium decide "enough is enough" and being the process to become a primary spermatocyte?

I think it does so once per germ cell division, but I am not sure. This is a histological/cell bio question. Certainly more in depth than the MCAT and passed my knowledge base. Sorry I can't be of more help!

 

[Czarcasm]

@sillyjoe

Okay so you have a spermatogonium which can do mitosis to make another spermatogonium.

Theoretically, this process could go on forever (making infinity spermatogonium).

At what point does any one spermatogonium decide "enough is enough" and being the process to become a primary spermatocyte?

The stem cell (in this case, the primordial germ cell) undergoes mitotic division to replicate itself. One copy will preceed through meiosis to become a spermatozoan and eventually fully mature as sperm. The other replicated cell stays behind to facilitate future mitotic divisions. Based on examples I've seen - this is true of all stem cells, even cells lining the gut as well (one differentiates, the other stays behind as a copy).