MEIOSIS ALL RAPPED UP
by Arthur W. Siebens, Ph.D., Copyright 1999

Keeping track of genes is one of nature's wonders
That's why you've got chromosomes-to avoid major blunders
Cell duplication's impressive, it's called mitosis
But you ain't seen nothin' 'til you've seen meiosis
Remember eggs and sperm are called gametes
Want to know how they're made? You're in for a treat!

Now meiosis takes eight steps instead of just four
'Cause there's two cell divisions1 we're about to explore
In prophase I a unique event happens
Homologous chromosomes join-its called synapsis2
Yes, when tetrads form, DNA can be swapped
So genes from Mom's chromosome are now on Pop's
This crossing over increases recombination
So there's no one like you in all the United Nations!
Chromosomes then line up in metaphase I
But what's important in anaphase (I) is what's not undone
That's the centromere, which remains unbroken
Homologous chromosomes move apart3-the products will be 1N (haploid).

So the chromosome number's down to 23
'Course that assumes you're a human like me
But each chromosome's got two chromatids
Which just won't work when making kids
So after telophase I and interphase II
The cell divides again--similar phase names are used
So there's prophase (II) and metaphase (II) and anaphase (II)
In anaphase II the centromere finally breaks4,*
So each sperm or egg gets only one copy
Of 23 chromosomes 5-can't afford to be sloppy
So after telophase II and cytokinesis
Meiosis is through and this little rap ceases.

1,2,3,4,5 Key differences between meiosis and mitosis.
* Chromatids are called chromosomes after the centromere breaks.