Nondisjunction on purpose: Reasonable?

Discussions on general biology and biological evolution, genetics, zoology, ecology, botany, etc.

Nondisjunction on purpose: Reasonable?

Postby caters on September 22nd, 2017, 3:59 pm 

In spermatogenesis in males or hermaphrodites when it comes to numbers as a species, the meiosis after the first division is asymmetric.

They have 6 types of chromosomes.

First, there are autosomes. These are only duplicated once and the chromatids separate once. From then on, only 2 sperm per secondary spermatocyte end up with these autosomes.

The other types of chromosomes can end up in any of the 6 sperm produced. Those are:

  • Sex Chromosomes(there are 4 sex chromosomes and each viable combination leads to a different result unless you are comparing XYYY to XXXY)
  • Operational chromosomes(These determine the value of the number, more specifically the first sperm to fertilize the egg detemines what operation is done)
  • Color chromosome(This is a chromosome specialized for color of all kinds and is specialized for color patterns as well)
  • Size chromosome(This chromosome determines the size of everything in the body based on mixed genetics(incomplete dominance in the middle, complete dominance towards the extremes for any given body part) and every gene affects the result, some more than others. So for example if the gene for the heart has the allele for extra small, than the whole body is going to be extra small regardless of the actual genetics for full body size)
  • Circular chromosome(This chromosome codes for very few genes, most of them having to do with nuclear proteins)
As an example here is 1 possible result for an XXXY male:

1st sperm produced from division: X, circular chromosome, color chromosome, size chromosome, multiplication chromosome, autosomes
2nd sperm produced: autosomes, Y, addition chromosome
3rd sperm produced: subtraction chromosome
4th sperm produced: X, division chromosome
5th sperm produced: nth root chromosome
6th sperm produced: X, exponentiation chromosome

Now, in the zygote, this will sometimes lead to triploidy of the autosomes and will always lead to 1 more sex chromosome than needed. Since triploidy is not viable in numbers and having an extra sex chromosome could cause problems, the egg cell carries with it DNase enzymes in the nucleus. These are only activated when needed to get rid of chromosomes. So with every zygote, the DNase is activated when there are 5 sex chromosomes so that the number doesn't develop any problems from having an extra sex chromosome.

But, is this nondisjunction a good thing in this case?
Posts: 176
Joined: 12 Nov 2013
Blog: View Blog (2)

Re: Nondisjunction on purpose: Reasonable?

Postby BioWizard on October 18th, 2017, 4:43 pm 

I don't understand several things about your post. Including "6 sperm produced", "size chromosome", "color chromosome", etc. Phenotypic traits aren't determined by chromosomes.
User avatar
Forum Administrator
Posts: 12581
Joined: 24 Mar 2005
Location: United States
Blog: View Blog (3)

Return to Biology

Who is online

Users browsing this forum: No registered users and 8 guests