meiosis reductive division

[chrisvocker]

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Is the 1st or 2nd meiotic division considered "reductive division"? I was thinking the first division is reductive since you are going from diploid to haploid. Kaplan says the 2nd is reductive. Is this a mistake or am I losing it?

Also, if the 1st division is "reductive", what is the second called?

 

[Anemone]

Is the 1st or 2nd meiotic division considered "reductive division"? I was thinking the first division is reductive since you are going from diploid to haploid. Kaplan says the 2nd is reductive. Is this a mistake or am I losing it?

Also, if the 1st division is "reductive", what is the second called?

1st=reductional
2nd=equational

 

[chrisvocker]

thank you

 

[Anemone]

thank you

de nada

 

[DentalKitty]

Is the 1st or 2nd meiotic division considered "reductive division"? I was thinking the first division is reductive since you are going from diploid to haploid. Kaplan says the 2nd is reductive. Is this a mistake or am I losing it?

Also, if the 1st division is "reductive", what is the second called?

I also learned that the 1st division is the reduction division in my Bio II class so I was really annoyed when Kaplan (the book and my teacher) insisted the 2nd division was the reductive one. However, even though my Bio II textbook clearly states that D1 is reductive, my Cell Bio textbook clearly states D2 is the reductive one and specifically mentions that D1 is not reductive. Go figure. I guess it is not 100% agreed upon. It is definitely frustrating though, and I don't think they would ask you that particular detail on the DAT. If they did you could probably challenge it.

 

[UJ007]

I thought meisois 2 was the reductive division. It goes from diploid to haploid in M2, no? Since Meiosis 1 is just like mitosis (with the exception of crossing-over that can occur etc) so you have replication of the chromosomes. In meiosis 2 you have them dividing without replicating. In meiosis 1 there are 2 diploid cells, after meisois 2 you have 4 haploid gamete cells. So wouldn't M2 be the reductive division?

 

[xtractime]

I thought meisois 2 was the reductive division. It goes from diploid to haploid in M2, no? Since Meiosis 1 is just like mitosis (with the exception of crossing-over that can occur etc) so you have replication of the chromosomes. In meiosis 2 you have them dividing without replicating. In meiosis 1 there are 2 diploid cells, after meisois 2 you have 4 haploid gamete cells. So wouldn't M2 be the reductive division?

that was also my rationale when i first read this post. however, i have also found the same disagreements in text as the other posters. o well, just hope on the DAT that they will only give one of the options so we don't the other one. 👎

 

[chrisvocker]

*feels like he is in high school intro bio all over again*

I am pretty sure that the 1st meitotic division is 2N -> N and the 2nd division is just like mititosis. This we can agree upon, no?

I have no idea how the 2nd meiotic division can be considered reductional...there's nothing "reducing" about it.

Also,

It is definitely frustrating though, and I don't think they would ask you that particular detail on the DAT. If they did you could probably challenge it.

Can you challenge questions on the DAT? I mean, what? you call the ADA and say, #33 on the bio portion, umm, I think you had the wrong answer? hahaha.
And, IMO, even though I havent taken the test yet, this question is really fundamental bio stuff and it feels like fair game.

 

[UJ007]

*feels like he is in high school intro bio all over again*

I am pretty sure that the 1st meitotic division is 2N -> N and the 2nd division is just like mititosis. This we can agree upon, no?

I have no idea how the 2nd meiotic division can be considered reductional...there's nothing "reducing" about it.

Crossing over occurs in meiosis 1, you need homologous chromosomes therefore each chromosome needs to be replicated which occurs in meiosis 1. So there is no reduction. In meisosis 2 you have to homologous chrosomes splitting but there is no replication, so that is where the reductive process occurs.
Meiosis 2 is just like mitosis but without the replication. So after meisosis 2 you have haploid cells.
What is the point of having a second meiotic division if you already achieved a haploid cell after the first meitoic division?

 

[chrisvocker]

Crossing over occurs in meiosis 1, you need homologous chromosomes therefore each chromosome needs to be replicated which occurs in meiosis 1.

I agree, crossing over is in prophase 1. The chromes are replicated in the interphase preceding this. Then the homologs pair up and separate (to two haploid cells)

In meisosis 2 you have to homologous chrosomes splitting but there is no replication, so that is where the reductive process occurs.
Meiosis 2 is just like mitosis but without the replication. So after meisosis 2 you have haploid cells.

Homologs have already splite before meiosis 2. But yes, there is still no replication

You are correct, you have haploid cells after meiosis 2, but you also have haploid cells after meiosis 1. Anyways, I think the reason that meisosis may have been labeled (read as 'mislabeled') reductive is that a 2 chromatid chromosome is being "reduced" into a one stranded chromosome. That is my only guess.

If you have Campbell bio book, look around page 240. Separation of homologous chromes occurs in meiosis 1, therefore 2N -> N. After this separation, the chromes still exist as two sister chromatids. Then, in Meiosis 2 the chromes get pull apart into single chromatids, but each daughter cell still has the same number of chromosomes, albeit they are unreplicated.

What is the point of having a second meiotic division if you already achieved a haploid cell after the first meitoic division?

I dunno....to get more for your money?

 

[UJ007]

My opinion... chances are this is not gonna show up on the dat

I dunno....to get more for your money?

Honestly, best answer so far!