Entendre el Nombre de Cromosomes en Mitosi i Meiosi

[Music] if you have ever studied mitosis or meiosis chances are the whole chromosome

number thing it's crossed your mind I mean how do you start out with a cell that has 46 chromosomes and then it does

mitosis and then you end with two cells that each have 46 chromosomes or in meiosis you end up with four cells that

each have 23 chromosomes it's like here's a chromosome there's a chromosome everywhere a chromosome chromosome but

how well this video is going to explain the chromosome numbers in these processes but please watch our mitosis

and meiosis video first so that you can understand the actual process first and also our video is talking about

chromosome numbers in human cells so please assume that for the entire video and just a reminder human body cells

have 46 chromosomes and human sex cells also Al called gametes they have 23 chromosomes now chromosomes as you know

they're made up of DNA and protein the DNA is highly condensed tightly wound that's really important because it means

that when the cells divide and they have to move that DNA over it's easy to do that when the DNA has condensed into

chromosomes it makes DNA so portable and organized which is great in processes like mitosis and meiosis because when

you make new cells you also have to get the DNA into those cells this is a chromosome this is also a chromosome the

difference is the first one only had one chromatid or copy and the second one has two chromatids or copies the area in the

middle of the chromosomes this is called a centromere and the centromere is where the spindle is going to attach and

that's kind of a big deal because that's how you're going to move the chromosomes during any division process now

generally when you count chromosomes you can count them by the number of Center mirrors present now interphase is a step

that happens one time before mitosis and meiosis can start and in interphase this is where we duplicate the chromosomes so

first we start with 46 of these chromosomes which is how many chromosomes are found in human body

cells and as you can see in our little picture they kind of look like little sticks but after duplicating in

interphase we still have 46 chromosomes technically but they have two chromatids we call them sister

chromatids and they're held together at one centor see as long as those chromatids are still attached at the

center mirror we still count 46 chromosomes but they're duplicated and if they weren't attached like this I

mean technically you could say there were 92 two chromosomes but right now in this picture there are 46 chromosomes

and 92 chromatids here's a little chart here cuz I love charts so is there a time in

mitosis when there are 92 chromosomes well technically you could argue that anaphase when the sister

chromatids are separating and they're no longer attached you could see in this picture there could be 92 chromosomes CU

they're not attached during that one phase and that's why our chart has a little

Aster here although we still usually refer to them as chromatids during this process of cell

division so at the end of mitosis those chromatids separate and you end up with two cells after mitosis that each have

46 chromosomes those chromosomes kind of look like little sticks in this picture the two daughter cells if you look are

identical to the starting cell in my Tois now let's take a look at meiosis we have 46 chromosomes in the starting cell

and right now they each have one chromatid just like with mitosis and they duplicated interphase and we still

have 46 chromosomes now and there are 92 sister chromatids just like we started with in

mitosis but at the end of meiosis 1 you have two daughter cells and they each contain 23 chromosomes with 4 six

chromatids at the end of meiosis 2 you have four cells that each have 23 chromosomes 23

chromatids just a reminder that in mitosis the resulting two cells are identical so they have the same number

of chromosomes as the original cell so the two daughter cells after mitosis have 46 chromosomes and they're

identical but in meiosis it's a reduction division the four daughter cells they have have the amount of

chromosomes as the original cell that's why each daughter cell after meiosis has 23

chromosomes so we hope that clears it up a little bit for you now just remember that chromosome counting it has a lot to

do with the way we count chromosomes and this definition of chromatid well that's it for the amoeba

sisters and we remind you to stay curious [Music]

[Applause] [Music]