How does crossing over during meiosis result in the "Unlinking" of linked genes?

"Linked Genes" basically means the genes are close in sequence on a chromosome....like neighbors.

Imagine you've got 2 books. They are "identical" - meaning two copies of the same book. These are like copies of your chromosomes. The sentences in these books are like genes, and you could say that sentences that are on the same page are "linked"....ie, close to each other.

The Meiosis process is complex, and there are good reviews (like wikipedia), but in cartoonish terms, imagine you take one book and open it to page 10, and you open the other book to page 11...get the pages wet, and the ink from page 10 smears onto page 11, then you pull the books apart. Now on one book, the sentences from page 11 are printed across page 10, and on page 11 of the other book there are page 10 sentences.

The page 10 sentences in one book are suddenly "unlinked", since they have page 11 sentences in them...and the same for the other book.

When the chromosomes separate in meiosis, there is a crossing over event and the pulling apart of the chromosomes can transfer genetic matieral from one chromosome to another. Since there are billions of nucleotides, they don't usually line up exactly, and this "sloppy" cross over unlinks genes due to the deletion/insertion from the other gene.

Hope that helps.