Inspired by Johnny Cash’s “One Piece at a Time.”
Scroll below the video for lyrics.
Meiosis, it’s how we make sex cells or gametes
The sperm cells or egg cells performing the feat
Of moving genes forward in eukaryotes like orchids and bees.
Meiosis doesn’t happen in all cells of the body
There’s just a few cells that have this hobby
I’m talking ’bout germ cells in testes and ovaries,
Germ cells are diploid and what that means,
Is that the chromosomes are paired up in teams
In each pair one’s from your dad, one’s from your mother,
And when you line up the chromosomes it’s suddenly clear
How each is a member of a coupled pair,
Homologous pairs, each a homologue of the other.
In humans, the diploid number’s forty-six,
And a key trick that happens in meiosis
is dividing that number in half to 23
And that single set of chromosomes has its own name
It’s called “haploid” in this meiotic game.
So diploid to haploid’s a key meiotic strategy.
Meiosis makes eggs and sperm
It’s the same in the robin as it is in the worm.
Makes haploid gametes with recombination,
Meiosis creates variation!
In interphase I meiosis starts,
It’s the DNA replication part
An evolutionary relic of its origin,
‘Cause meiosis evolved from mitosis you see,
So each process starts identically
Replicating chromosomes into two sister chromatids.
In Prophase I chromosomes coil up, and homologous pairs pair up,
Forming tetrads, each with chromatids four.
A chiasma’s the spot where the chromatids link
And synapsis is the name for the whole darn thing,
And crossing over is what this whole process is for.
See the homologues aren’t identical twins– no way!
They’re not the same DNA
The genes are the same but the alleles might take different forms,
So during synapsis alleles can cross over,
Between homologues, and when it’s all over,
There are gene combinations that have never been seen before.
Another meiotic variety creator,
Is metaphase one with homologues at the equator,
Cause how each pair lines up is random and independent,
So in one pair facing north might be the maternal,
In the next one, it might be the paternal,
It’s a one-in-two shot, it’s called independent assortment.
So two pairs divide up in four distinct ways,
It’s two to the number of pairs, you could say.
So think ‘bout us humans with 23 homologous pairs
Two to the 23rd power is a number so great,
Is 8 million, three eighty-eight thousand, six-oh-eight
That’s why metaphase one is a variety-creating affair.
And now connect this assortment with recombination,
Note that what we’ve got during gamete creation.
Is sperm and egg cells that are absolutely unique
So if you ever wondered why sisters or brothers
Can be so different from one another
Just remember these meiotic recombining techniques
And if meiosis had never evolved
The book of life would be a different tome.
Cause if it wasn’t for meiosis
All offspring would be clones!
Metaphase one: homologues at the equator
Anaphase one: they say “see you later”
It’s like Mom and Dad splitting up and setting up new homes.
Two nuclei form in telophase one,
Then cytokinesis, meiosis one is done,
We’ve got two haploid daughters, still with doubled chromosomes.
Now things are simpler in part two of meiosis
Essentially it’s like just mitosis,
You just need to pull those sister chromatids apart,
They line up in the center in metaphase two
Anaphase pulls them apart we’re almost through,
Telophase then cytokinesis, we’re at the last part.