daughter cell of meiosis I

[m25]

Why is the daughter cell of meiosis I considered to be a haploid rather than a diploid? Like, how are haploid and diploid defined in terms of the MCAT?

And since the haploid daughter cell of meiosis I looks like X and the diploid cell in mitosis also looks like X , then does that mean when we are presented with a diagram that looks like X on the MCAT, we cannot tell if it is 2N or N without first knowing if the cell is going through mitosis or meiosis, correct?

And in terms of the MCAT, do human cells ever have 4N in it's life cycle?

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[Hadi7183]

What you see as "X" after meiosis I is a pair of sister chromatids and not a pair of homologues. Only the latter corresponds to a diploid cell, because two DNA strains are not identical. A pair of sister chromatids, even though they have gone through recombination and slightly changed, are technically considered to be same even if you physically see two strains. Having a pair of sister chromatids doesn't mean diploidy.

And I guess prior to meiosis I, germ cells briefly exist as 4N state.

 

[AwayFromReality]

The whole replication process, the way I understand it, is this:

Normally humans have 46 chromosomes in 23 homologous pairs (Diploid)
Replication increases to 96 chromosomes in 46 homologous pairs(Diploid). The 46 pairs that you have are made up of two X joined together, forming a tetrad XX.
Meiosis I goes through and you now have 46 chromosomes in the form of X (which is known as a Diad). You are now Haploid.
Meiosis II proceeds like mitosis, giving each germ cell 23 chromosomes (Still haploid). Each cell has a chromatid from the diad so X breaks up into | and |.

Therefore, for the purposes of the MCAT, diploid means that there are homologous pairs. If you don't have homologous pairs you are haploid.

PS: This is what I understood from my studying, if I am wrong someone please explain it to me