Biology Question

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[jcb123]

So upon ovulation the first meiotic division occurs.
Then the sperm comes along and fertilizes the egg. This fertilization triggers second meiotic division and polar bodies are created.

I think that pretty much gets at the part that's confusing you.
Like always anyone please add corrections or more info if there's something I missed.

 

[brood910]

So upon ovulation the first meiotic division occurs.
Then the sperm comes along and fertilizes the egg. This fertilization triggers second meiotic division and polar bodies are created.

I think that pretty much gets at the part that's confusing you.
Like always anyone please add corrections or more info if there's something I missed.

Partially correct.

When sperm enters the cytoplasm of oocyte, oocyte gets through the 2nd meiotic division and becomes an ovum.
Ovum + sperm = fertilization.

 

[dyspareunia]

Partially correct.

When sperm enters the cytoplasm of oocyte, oocyte gets through the 2nd meiotic division and becomes an ovum.
Ovum + sperm = fertilization.

Incorrect. Sperm + secondary oocyte = fertilization.

Fusion of the two pronuclei occurs after the second meiotic division, which occurs after fertilization. Only after the second meiotic division does the thing become called the ovum.

The sperm comes along, breaks down the granulosa lutein matrix, then penetrates the zona pellucida, then the cortical reaction, then fertilization, then completion of the oocyte meiosis 2, then the pronuclei fuse.

 

[brood910]

Incorrect. Sperm + secondary oocyte = fertilization.

Fusion of the two pronuclei occurs after the second meiotic division, which occurs after fertilization. Only after the second meiotic division does the thing become called the ovum.

The sperm comes along, breaks down the granulosa lutein matrix, then penetrates the zona pellucida, then the cortical reaction, then fertilization, then completion of the oocyte meiosis 2, then the pronuclei fuse.

? You are saying exactly what I said except for secondary oocyte + sperm = fert.

You should read bio books again.

A direct quote from EK bio book:

"The entry of the sperm causes cortical reaction, which prevents other sperms from fertilizing the same egg. Now the oocyte goes thru the second meiotic division to become an ovum and releases a second polar body. Fertilization occurs when the nuclei of the ovum and sperm fuse to form zygote".

You can find the same information in TBR + TPR Bio book.
So, actually, the second meiotic division occurs before fertilization.

 

[dyspareunia]

So, actually, the second meiotic division occurs before fertilization.

No. That's wrong.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3491123/
http://www.ncbi.nlm.nih.gov/books/NBK9901/
http://www.ncbi.nlm.nih.gov/pubmed/18084010
http://www.nature.com/nrm/journal/v14/n9/fig_tab/nrm3643_F2.html

Secondary oocyte is suspended in metaphase II until fertilization occurs. Fertilization triggers completion of meiosis II.

However, you're free to go with what EK and TBR says. I'm sure that the AAMC ignores the literature and instead writes MCAT questions based on what MCAT review books say.