I'm trying to understand ploidy and something is not making sense to me. can anyone help?

 

wheat (Triticum aestivum) has haploid number n=21 (there are 3 copies of each type of chromosome in the gamete, so the monoploid number, x=7)

 

its somatic cells are described as having 2n=6x=42 chromosomes. (double what is in a gamete or 6 copies of the 7 different chromosomes)

 

This makes perfect sense to me except for the 2n part. I thought that 2n implied that a cell is diploid (i.e. two sets of chromosomes) but the wheat cell has 6 sets of chromosomes. So apparently I don't understand what 2n really means. What would be an example of something that is 6N??

 

 

I was able to find the answer to my question.

In case anyone else cares-

 

2n does not necessarily mean that a cell is diploid. The x refers to the ploidy (the n doesn't refer to the ploidy)

 

n is the number of chromosomes in a gamete

2n is merely twice that number (what you end up with when 2 gametes fuse)

 

3n is three times the haploid number of chromosomes (what you get when 3 gametes fuse). Wheat endosperm has 3n=63 chromosomes (created from the fusion of one sperm cell and two polar bodies).