Question

The table below provides the number of chromosomes found in the body cells of various types of organisms.





Diploid Chromosome Number





Fruit Fly


8




Human


46




Goldfish


94


Which of the following is the best explanation for why the chromosome numbers above are all even? Answer







Animal cells always have an even number of chromosomes, and plant cells always have an odd number of chromosomes.








The number of chromosomes present in a diploid cell doubles for each generation because there are two parent

Answer 1

I'm assuming that this is a multiple choice answer and that the answers are the two last statements. I'm only saying this because, if it were and option, I wouldn't choose either of the answers. The one about animal cells being even and plant cells being odd is just plain wrong. The other option is, at best, terribly worded. Without the context of the question, I would just assume that the statement were nonsense and not actually a correct answer with awful wording.

That being said, if I were presented with just these two answers as options, I would choose the second: The number of chromosomes present in a diploid cell doubles for each generation because there are two parent.

The statement is itself wrong in that it suggests that each generation will result in a doubling of the chromosome number. If that were true, the diploid cells for fruit flies in generation 1 (G1) would be 8, G2 would be 16, G3 would be 32, so on and so on...
This is not the case.

What I think the statement is trying, and horribly failing, to state is that the diploid cells of these organisms all arise from the combination of haploid sex cells. The somatic cells of these organisms are diploid, essentially meaning they have two sets of chromosomes. Sex cells, on the other hand, arise from meiosis which results in them being haploid, only having one set of chromosomes. In order to form the beginning of an embryo, two sex cells have to combine; thus the two haploid cells combine forming a new diploid cell which will go on to become the next generation offspring. The number of chromosomes in the diploid cells is always going to be even, because it is the result of a two haploid cells combining. 2 x any number will always be even.

Put into a drawing:


2n must always be an even number.