Showing posts with label cytokinesis. Show all posts
Showing posts with label cytokinesis. Show all posts

Sunday, 28 January 2018

Hour 17: Mitose-me

Dear diary,

I found myself lying there, surrounded by darkness and fog. I couldn’t remember who or where I was. I couldn’t feel my body. And then, as if in a dream, a memory came to greet me. It was an old memory, of when I had just been born. It’s contours felt fuzzy, but the words I had over-heard remained sharp. An older cell had been singing its last truth before giving in to senescence, telling a tale as old as tales go. The words rang in my mind as I remembered. I could see it now.

''Legend says mitosis is not a cellular process, but the story of two lovers. As with every epic love story, there was a great love, unfounded jealous, and an eternity of punishment. But there cannot be a love story without a slither of a happy ending. Even here, the two lovers found a way to be re-united, if only for an instant, during mitosis.




This love story begins in something smaller than the human cell: the cellular nucleus. It’s a story that begins at the beginning of all things, where two sets of chromosomes who had always felt like they were halves of something bigger, finally met. The love that ensued was bigger and stronger than all things. Not bearing the thought of separation, the two lovers decided to let their encasing membranes fuse, and become one. Enclosed in the same nucleous, nothing could keep them apart. For a while all was well, and they continued to live surrounded by each other, their searching appeased, their souls content.




But gradually things began to deteriorate: All the other cellular organelles started to become jealous. Having been forced into a life of solitude, never to find another’s half, they wallowed in their loneliness as they gazed into the happiness of the chromosome pair. Bitter and resentful, they knew the cell needed the double set of chromosomes to survive. Instead,  their vengeance was inflicted disguised as a gift: The chromosomes were to be granted their wish to always be together but forced to fuse to create one full set of genes. The curse caused the chromosomes to be torn to pieces as they merged. When they became one, the power of their love was so strong that it gave life, and the first cell was born. But it came at a cost: The chromosome lovers had been forced into unity, losing their identity. They had been morphed into eternal solitude. Their love became a distant memory.

Eventually, nature took pity on the chromosome lovers, and decided to reward them for their sacrifice of life. And so, mitosis was born: During mitosis, each chromosome is duplicated into an identical copy. Then, and only then, are the chromosome lovers able to see each other again. For a fleeting glimpse of an instant, they are left to be individuals, to gaze in wonder, to speak, to love. To keep all the other organelles at bay, nature distracted them by allowing them to become doubled too. Thus, even if for a short time, mitosis became the time when all solitude was lost, as each part of the cell finally found its other half. 


As is every other cellular process, mitosis was designed to have different phases. Like clockwork, each phase was to progress into the next, eventually ending in two separate cells, each with it's own set of chromosomes, an unavoidable conclusion to a temporary solace. But at first, things didn't flow smoothly: Finally re-united, the doubled chromosomes clung to each other, refusing to lose each other again. They held on, a promise in their cores, creating a bond that is now known as the  kinetochore. To this day, mitosis will reveal the chromosomes connected at their kinetochore as strongly as the interlocked fingers of obstinate, desperate souls. Centrosomes were therefore devised, small centres that could create and control rope-like microtubules.  



During prophase, the first phase of mitosis, the microtubule ropes were unleashed and ordered to go and bind each chromosome at the centre of their souls, the kinetochores, and begin pulling the couple apart from other ends of the cell. The unyielding, unrelenting strength of the microtubules was such that the second mitosis phase, the metaphase, was punctuated by the scene of all the chromosome couples, still together, but aligned in the centre of the nucleous. The love and sorrow ensuing from that one moment was such that it earned its own name, 'the metaphase plate', the platform of halves. All bonds were finally broken in the next phase, called anaphase, during which the lovers were separated and dragged into opposite ends of the cell. Their songs of woe will be enough to pierce your soul, each and every time. When telophase finally rang true, the separated chromosomes found themselves encased in separate sets of membranes, each containing one copy of a full set of genes. Finding no solace in their renewed solitude, the chromosomes melted into undefined chromatin, leaving behind the definition of a shape, of an identity, unable to bear life alone. Mitosis ended with cytokinesis, where a cell splits into two, each side claiming a set of organelles, and a nucleous of implacable sorrow. 

Thus, mitosis became the curse of true lovers, the penalty of jealousy, the loneliness of nature, the sacrifice of life.''

I felt it then. I felt my membrane and my organelles, my double personality. I felt too full, like I was going to explode. And then a tear, right in the middle of my membrane, and I felt release. The tear grew bigger and bigger, and I wondered if I was meant to feel scared. But it was strangely pleasant, satisfactory somehow, like removing dead skin from your body. I felt it rip me in half, and I let it, feeling more and more myself until finally, it was over. There was nothing more to tear, there were now two membranes, two minds. I was me again, just me. Tiny, insignificant, happy to die trying to change, me. 

'Welcome back' whispered a familiar voice. And I smiled.

Cell X

Monday, 16 March 2015

Hour 2: The cycle of life

Dear diary,

Time seems to pass by in a flurry of diffusion and CO2 release. All is quiet except for the distant rhythmic pulsing of the nearby blood vessels and the occasional bustle of sporadic oxygen molecules. I wish I could describe the amazing landscape that surrounds me, with the synergy of cells working in unison to create…well, life. But unfortunately all I see is pitch black. I can only distinguish my whereabouts by the different squidgy sounds different organs make when I accidentally brush against them.

All my neighbouring cells seem to be interested in is proliferating. You will find them sticking out their membranes with an air of superiority, importantly announcing to whoever is in their vicinity that they are about to enter the M-phase. The ‘M-phase’! They won’t even call it by its full name (mitosis) because they say only newly-split cells call it that. For those human readers that are not cells, mitosis is the step where cells finally manage to divide themselves into two identical copies. I mean, talk about being narcissistic! Luckily, mitosis is not as easy as it sounds…cells first have to go through the G1-phase (they call it the ‘growth phase’, but really, they just get fat), then the S-phase (there they get to copy all the crappy stuff that is in their heart, or nucleus…like DNA), and then another growth phase called G2 (the cell’s equivalent of putting on weight, then stuffing its face more because the diet starts tomorrow). Only once they’ve done all that, do they get to enter the M-phase. But don’t worry, none of them are actually splitting. Nutrients and oxygen are too scarce lately, and most of us wouldn’t be able to reach G1 even if we wanted to!

Sometimes, you will find a cell sneakily pinching its mid-riff and, with an irritating air of supremacy, whisper in a strained voice that it is time, it’s undergoing cytokinesis. These types of statements are usually acclaimed with a tense silence, bursting with a mixture of jealousy and curiosity. Yet, when after several minutes the cell is still formed by one intact globule, with no trace of a contractile ring, most cancer cells will begin to call its bluff. The shamed cell will then have to admit to still having a single nucleus, and resume its plump shape. Believe it or not, cytokinesis is the step after mitosis (I know, life is complicated for us cells)…just picture it as the phase where the cell is now as gigantic as a sumo wrestler, complete with double everything (organelle wise). Now picture a person coming along and placing a really skinny belt on the belly of this gigantic sumo, and insisting on tightening the buckle until the sumo actually splits into two. Well there you have it, cytokinesis.

As usual, nobody pays me much attention except for those rare glances at my chromatin (I really need to comb that DNA of mine), just to make sure I will not suddenly split myself into two and beat them all at it. Not that I have any intention of doing so. I don’t really understand their fascination for constantly bloating and splitting. Imagine your biggest aim in life being to split into two? No thank you, I am perfectly comfortable sticking to my Go-phase (the phase where you don’t bloat, and instead look toned and gorgeous).

I wonder if one day I’ll become just as pointless as the rest of them. They told me it’s the ‘cycle of life’. I guess only time will tell.  


Cell X