FH
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Can anyone please explain in detail the process of Mieosis and Mitosis.
It seems to me that whatever I know about it is not enough!!
I know that Meiosis gives rise to 4 daughter cells, while Mitosoit doubles.
its not enough to knoe that in The embry stage the ova are arrested in the Meiosis 1 in Prophase and at puberty they are arrested in the Metaphase of 2nd Meiosis.
Please Help!!
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| mjl1717
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Ill attempt meiosis.-In meiosis 1 centromeres Do NOT split-we get 2 secondary gametocytes (23 duplicated chromosomes-2N)
In meiosis II centromeres split 4 gametes (23 single chromosomes 1N)
In the femaleprimordial germ cell arrive at ovary at 4 wks- oogonia
oogonia give rise to primary oocytes
**ALL PRIMARY OOCYTES ARE FORMED BY 5TH MONTH OF FETAL LIFE**
primary oocytes are dormant in prophase 1 at least until puberty. After puberty only one primary oocyte will reach maturity with each cycle
After puberty the primary oocyte completes meiosis 1 to form 2 daughter cells the SECONDARY OOCYTE and the first polar body.
The secondary oocyte enters meiosis 2when the chromosomes align at the metaphase plate,ovulation occurs.At this point ovulation is completed in the uterine tube.
AS STATED THE SECONDARY OOCYTE IS ARRESTED IN METAPHASE OF MEIOSIS II UNTIL FERTILIZATION OCCURS.
At fertilization the oocyte will complete meiosis II to form a mature oocyte and a second polar body.
#s of primary oocytes
7 million primary oocytes at 5 months of fetal life
2 million at birth
40,000 at puberty
#s of secondary oocytes
12 are ovulated per year(up to 480 over the reproductive life(40 years)
( this # is reduced in women taking OCP)
Pause :cry: :idea:
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| meg
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the specific prophase phase when the primary are arrested is diplotene/dictyotene.
Leptotene - chromosomes begin appearing
Zygotene- homologous chromosomes start pairing
Pachytene- finish pairing
Diplotene/dictyotene- Chiasmata visible as homologous chromosmes start repelling
Diakinesis - nuclear membrane disappears
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| FH
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Thank you both.
Can we go a little bit further backwards? I mean can you start at all the stages and events of MEIOSIS (NOT in respect to oocytes), like the process of MEIOSIS itself, so that I have a clearer picture of whats going on (I have definately forgotten my basics!!)
thanks! :oops:
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| meg
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Okay, Basically whether Meiosis or Mitosis,the basic stages include
1) Prophase:- the nuclear membrane disappears, the chromatin become visible as distinct chromatin.
2) Metaphase:- the chromatin arrange themselves at the middle of the cell (equatorial region)
3) Anaphase:- the chromatin move to the poles
4) Telophase:- nuclear membrane is formed and 2 cells formed
In Meiosis, there are 2 steps:- Meiosis 1 and 2 (which is same as Mitosis)
The Meiosis 1 results in reduction division (that is if the cell was 4N , then each daughter cell is 2N). Then Meiosis 2 is equatorial division( here, the daugther cells become 1N).
Prophase 1 has 5 steps as I have mentioned earlier
So just remember that in the cell cycle, after G1, there is duplication of DNA and Centrioles in S phase, then after G2, as the cell enters division, based on whether it is somatic or germinal, it enters either mitosis or Meiosis.
I know this is real confusing, I am amazed that I am actually writing the steps because a few weeks back, I was totally SCARED about this. But I picked up NMS genetics, and Kaplan genetics, also I read BRS cell biology for this and I feel I am little better now. So basically , keep reading different books for this as they will use different words to explain and some way of explaning would make more sense.
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| FH
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Thank you meg. I finally get it , u did a good job of explaining the steps. I was not well informed to as to where to read this topic, do not have Kaplan notes yet so was very confused.Thanks again 
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| asmi
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Wow you know alot mjl!
Which book are you following for histo :?:
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| mjl1717
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BRS Histology., I have Ham as a reference (I took histo at Boston University.), Histology atlas by Gartner and Hiatt which I never look at, Hi Yield Histology, and Histology and cell biology "Pre Test"
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| mjl1717
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Addendum-- But Im small, not really worthy of comments like that .:icon_study:
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