Question about Meiosis !

[Kobebucsfan]

A cell that has just completed interphase and has not yet begun meiosis I has _______________ the amount of genetic material as a gamete derived from the very same cell.

Why is the answer: 4 times

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[ktran17]

The sister chromatid replicated. therefore you begin with 4x the amount of dna

4x -> 2x +2X -> X+ X +X +X

However, if you're looking at number of chromosomes it goes 2N -> N +N -> N+N +N+N

The amount of DNA and the number of chromosomes are different depending on what stage of meiosis/ mitosis you're talking about.

To count number of chromosomes, just count number of centromeres

 

[NDPitch]

Well, a cell has 2 copies of each chromosome right? Okay, easy enough. But, Meiosis produces 4 gametes from one parent cell. So, it first duplicates its existing chromosomes, and there are at this point 2 chromatids per chromosome. In Meiosis 1, these line up on the metaphase plate and divide, creating 2 haploid cells. In Meioisis 2, those 2 daughter cells divide again, and those two chomatids are pulled apart into separate chromosomes. Take this diagram for example. The square brackets indicate individual cells. The pipes are chromatids, and the tildes indicate where those chromatids are joined together on the same chromosome.

Before Meiosis... [ |~| |~| ]

After Meioisis 1... [ |~| ] [ |~| ]

After Meiosis 2... [ | ] [ | ] [ | ] [ | ]


Kinda hard to see through a text diagram I know, haha, but I hope you can see that the parent cell has 4 times the amount of genetic material as each daughter cell (gamete).

 

[chax1]

If the organism is diploid (2N) before it goes through any divisions, it needs to make copies of the DNA so whether its meiosis or mitosis the organism will always be 4N after interphase. Or you can look at it as, in order to make 4 haploid 👎 gametes, you need to divide the parent cell in 4, so logically if you want four cells with N, you need the parent to be 4N.