23 chromosones from each gammete, 23 pairs in a human cell. Doesn't make sense!?

Question

As far as i understand (no very much) a human cell contains 23 pairs of chromosones. But i am also told during fertilisation we have 23 'non-paired' chromosones in each gamete which eventually mix. That doesn't make 23 pairs though- it makes 46 seperate chromosones,

I'm CONFUSED.
Any help would be greatly appreciated. Thanks!!!

Answer 1

A normal cell does indeed have 23 *PAIRS* of chromosomes. Think of them like dance partners in a dance competition, where both partners in a pair have the same number pinned to their back (pair #1, pair #2, pair #3 ... up to pair #23).

During 'meiosis' the pairs split up. It's like the dance partners are given instructions to split up and go to opposite sides of the room. So now you have have 23 chromosomes (unpaired partners) with numbers 1, 2, 3 ... 23 on their backs on one side of the room (the cell), and another set (also with 1, 2, 3, .. 23 on their backs) on the other side.

The two sets of unpaired dance partners (unpaired chromosomes) are then loaded up on two buses (two sperm cells) and driven to another dance competition to get new partners (who have also been split up in the same way ... this represents the female reproductive system where meiosis has produced female gametes (egg cells) in the same way). Only the first bus (sperm cell) to get there gets to go inside (all other buses/sperm cells are out of luck). The first bus pulls up to the new room (egg cell) and unloads its 23 passengers into the room (fertilization of the egg cell), and each dance partner finds its counterpart with the same number on the back (its corresponding, or 'homologous' chromosome).

The result, now 23 new dance pairs (paired chromosomes). Not 46 separate chromosomes).

{P.S.}

Actually, meiosis is a bit more complicated that I describe here. Before meiosis, each chromosome first gets duplicated ... and the end result is not two sperm cells, but four (likewise with egg cells). So my description above is just for purposes of explaining *pairing*.

Answer 2

Yes, each living cell in your body has its own set of 23 pairs of chromosomes. They're the same in every cell, though, so when talking about genetics, we can treat it like your entire body has 23 pairs. In other words, Chromosome 3 in a cell in your arm is exactly the same as Chromosome 3 in a cell in your brain. That means that I can talk about a gene on Chromosome 3 without having to specify which cell, tissue, or organ it comes from. The expression of the gene (whether the gene is turned "on" or "off") will differ from cell to cell, but the actual chromosome itself is the same.

Answer 3

The complement of the human karyotype is 46 chromosomes in all the cells of the body except the gametes, in which there are 23.

Answer 4

23 pairs of something is 46 individuals of something..... so during fertilization you have 23 chromosomes from your mother and 23 from your father.... when they pair up you now have 23 "pairs" and thus 46 individual chromosomes.