As you might already know

Meiosis is the process in eukaryotic, sexually-reproducing animals that reduces the number of chromosomes in a cell before reproduction $^{[1]}$

One of the reasons why meiosis has been so important in evolution is variation.

As my teacher used to say: Nature rolls the dice... - It's the magic of genetics; two completely different persons might share the same parents.

So here the question:

enter image description here

Suppose we have a cell with four chromosomes (two couples of homologous chromosomes) in the Prophase 1. I've drawn all possible combinations that could happen - these are chosen randomly - in the Telophase 1.

Is there a genetic disorder (not only regarding humans), in which the four initial chromosomes are split, in the Telophase, into two parts, each of them containing a couple of homologous chromosomes. I.e. (referring to the image) is the combination $(\color{red}{red}+\color{blue}{blue})(\color{green}{green}+black)$ in the Telophase 1 possible?

$$$$ $^{[1]}$ Quote from https://biologydictionary.net/meiosis/


1 Answer 1


Failure to properly separate homologous chromosomes during meiosis, either by including an extra copy of a chromosome or including zero copies of a chromosome, causes gametes that are 'aneuploid', and as a result, a zygote that results from that gamete will have an extra or missing chromosome as well.

For humans, most aneuploidies are completely fatal at some point of early development, so there is not an associated genetic disorder in live births.

One common aneuploidy that is not fatal to the embryo is an extra copy of chromosome 21; this causes Down syndrome.

  • $\begingroup$ Thanks, @Bryan Krause [+1]. However, what I meant with the question was, if homologous chromosomes (here red+blue and black+green) could stay together in Telophase 1 (which isn't normal (or even possible???) but might be a genetic disorder) $\endgroup$
    – Dr. Mathva
    Apr 2, 2019 at 19:59
  • $\begingroup$ @Dr.Mathva I explained what the result would be if/when this happens for even 1 chromosome pair, which would lead to a genetic disorder in the offspring. A genetic disorder where all of your own germ cells failed to go through meiosis properly would effectively mean sterility because nearly all their gametes would be aneuploid, and most lethally so, so such a trait would not be passed to offspring. $\endgroup$
    – Bryan Krause
    Apr 2, 2019 at 20:09

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