They're these two kind ofĬylindrical looking structures. Centrioles are actually, they help, they are exist inside the centrosomes. And you might have heard of the word, let me label this again. Our centrosomes are at opposite ends of the cell at this point. Magenta in real life, I'm just making it a magentaīecause it looks nice. And then, here's the magenta, one of the magenta sister chromatids and another one. Here's another sister chromatid and they're connected at the centromere, not to be confused with a centrosome. So you have the blue one right over here, the blue one that's one sister chromatid. And the chromosomes start lining up in the middle of the cells. In the next phase, your nuclear membrane is now gone. Kind of the condensed form of the chromosomes. But anyway, this first phase of mitosis, the nuclear envelope, the nuclear membrane starts to disappear. Happen when they should happen and by what mechanism and Understanding exactly how do the different things Process is well understood but scientists are still And a lot of what I'm talking about, the general overview of the It kind of knows what to do even though it has no intelligence here. It's amazing that the structures, and what sometimes weĬonsider to be a simple thing but it's actually This is all happening throughĬhemical and thermodynamic reactions and the way, justīased on certain triggers of where the cell is and its life cycle. Happens and then that happens.' Remember, this cell doesn't have a brain. Over here and one of them is maybe going to go over here. And these two centrosomesĪre starting to migrate to opposite sides of the cell.

And the nuclear membrane starts to go away. So they're condensing nowĪs we enter into mitosis. Once again, it's nowĬhromatid right over there.

It was still considered, the magenta stuff was stillĬonsidered to be one chromosome. Sister chromatids combined are considered to be one chromosome. And it has the centromere that connects these two sister chromatids. It's gonna have kind of that classic chromosome shape It might look something like this if you were to look in a microscope. So for example, that magentaĬhromosome which is now made up of two sister chromatids They're all spread out to kind of a more condensedįorm that you can actually see from a light microscope. Go from being in their chromatin form where Mitosis involves the cell and I might draw a littleīit smaller just so I have enough space here. We have this big cell, ourĭNA has been replicated. Leave the end of interphase right over here. We get into cytokineses which will then split each of the nuclei into a separate cell when Will turn into two nuclei that each have the original Mitosis is the process by which this one nucleus And now, we're gonna talkĪbout the actual cell division. We talked about interphase which is the bulk of aĬell's life cycle as it grows and its DNA replicates,Īnd it grows some more. To see the Caenorhabditis elegans chromosomes:įinally, the appearance of chromosomes changes dramatically depending on the method used to visualize them - for some examples see:ĪDDENDUM: The cell-cycle stage also has a huge effect on the appearance of chromosomes. the nematode Caenorhabditis elegans) don't have localized centromeres, which makes their chromosomes look like bars rather than a variation on an X-shape. (This is actually from someone with Down syndrome.) To see the variety of shapes in the human karyotype (collection of chromosomes): This wikipedia article has a decent diagram and describes the complicated nomenclature (naming) for these different shapes: This means that that when you look (after staining) at the condensed chromosomes in a cell you can see chromosomes with chromatids that look like they only have one arm, others that have one long and one short arm, and some that will look like the two arms are of equal length.

Yes - the centromere can be located anywhere along the DNA strand.

Mitosis vs meiosis in humans