Audio Transcript Auto-generated
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so crossing over is the first event that leads toa
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genetic variation in the sperm, and the egg on as
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a result, causes genetic variation in the living organisms that
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undergo sexual reproduction, such as humans.
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Now what is the second event that happens in yours
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is one.
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In the first division.
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It's the independent assortment.
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Assortment means arrangement or organization.
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So during independent assortment the chromosomes during metaphors when they
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want to separate, they separate in a random fashion.
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Remember that we are speaking about 46 chromosomes separating 23
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to 1 cell until 23 to the other side.
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The separation it has no ruled, unlike my toes is
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the chromosomes at one side would stay at one side,
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and the chromosomes at the other side will move to
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one side.
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No, the separation in Moses.
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It happens in the random fashion, and there is infinite
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possibilities off how this separation is going to happen.
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And again, independent assortment that happens during an a phase
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one in the first division of during Moses contribute as
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well. So the genetic variation that is one off to,
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in addition to crossing over, that leads to changes among
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living organisms that undergoes sexual production.
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So if you look at this image, you can see
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here we are speaking only about three chromosomes.
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These three chromosomes have 64 different ways off separation.
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Okay, if you check the color, I can make for
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different ways off separation of chromosomes.
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Imagine. We have 46 chromosomes.
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How many possible divisions we might have?
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It's a lot.
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So crossing over and independent assortment are two events that
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lead to genetic variation on.
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They happened during the first stage off.
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So this is an overlook, Um, Overall, look on yourselves.
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As we said, divided into two stages is one, and
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we also stow is one includes pro fes meta face
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on a face and tell a face on.
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This division is called reduction and Division because it allows
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for the reduction of the number of chromosomes in each
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daughter cell.
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As a result, at the end of this cell, I'm
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going to have at the end of this division, I'm
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going to have to cells each having 23 chromosomes.
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The second division is Moses to also we call it
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the equation.
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Allow division on dhe muses to resembles my toes is
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where the two daughter cells.
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Each one having 23 will undergo one more division, resulting
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in four cells.
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Okay. And again, here we have pro face meta face
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and a face on tele face.
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It's very important to know that the way neurosis starts
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is the same as my sources starts.
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What I mean is there is interface here and there.
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So germ cells must undergo interface at the beginning.
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In the go nuts or the reproductive organs, they have
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to undergo G one s G to D n.
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A must be copied.
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They have to prepare correct mistakes.
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All the steps during interface must be done.
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Now, after that will start in a pro phase one
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profit phase one and phase one to phase one.
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After that directly, it will move toe Sisto with no
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interface. So there is one interface and two divisions.
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As a result, I will have four daughter cells.
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In order to understand the horses, we have to look
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at each phase alone, starting with the pro face improve
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phase. There is, um there is binding off chromosomes.
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That doesn't happen in my toes is called synapses.
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Synapses means the parent, the paternal and maternal chromosomes the
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line up together as home awards This image.
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It's not common in my horses and my horses.
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Chromosomes. They don't match together or they don't pair together.
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This sparing will cause the formation off something called T
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trot. The track is having four kilometers beside each other.
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I mean one chromosome onto chromosome, each having two parameters
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so four kilometers beside each other.
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This is important.
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Why it's important in order for crossing over toe happen.
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So for crossing over toe happen, the chromosome must be
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very close to each other.
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For this reason, this stuff happens during pro phase one,
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which is the first phase in Moses, and this is
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called synapses synapses off chromosomes.
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As a result, they will be able to undergo crossing
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over. Now, after crossing over is done.
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Other events in pro phase one are similar to my
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toes is where the nuclear membrane disappears that spindle fibers
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are formed from the century roles.
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Then we moved to the second phase, which is meta
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meta phase one.
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During meta phase one, the chromosomes line up in the
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middle, but they don't line beside each other the line
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up above each other.
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What? I mean is after the formation off the Tetra
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or the four Chromatis or the two homologous chromosomes.
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Together they will.
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They will line up as purse above each other in
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the equatorial plate or in the center of the self.
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For this reason, during any phase, the separation will be
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for the chromosomes, not for the parameters.
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As a result, in this example, we have six chromosomes
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in the cells.
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Three chromosomes will move to one side on other three
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will move to the other side.
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And again remember, during NFS.
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One independent assortment takes place, so the division off the
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chromosomes is very random on.
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It's not based on a constant or certain rules, so
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the paternal and the maternal chromosomes are B will be
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separated in a mixed virgin.
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I might have in oneself more paternal chromosomes and the
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other son.
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More maternal chromosomes on this will justify the fact that
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sometimes you have traits more trades coming between you and
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your father, and sometimes you have more trades coming between
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you and your mother.
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Because the sperms can carry mixed information, it's not exactly
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half 50% 52% from your father.
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Due to the fact off we have crossing over and
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we have independent assortment.
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But when we mean half the number of chromosomes, yes,
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it's 23 from here, 23 from there.
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But this chromosomes might be recombinant chromosomes.
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It means the same chromosome that you're getting from your
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father is having a segment from your grandfather.
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A segment from your grandmother.
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So there is a combination between the information.
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So by the end off is one I'm having after
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tele face and psychokinesis two cells, each one having one
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on chromosome.
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What I mean by one and chromosome.
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It means 23 chromosomes.
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Okay, now, after that, uses to will happen directly after
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Moses, one on DME uses to.
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As we said earlier, it's similar to my sources.
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So these two cells, now each cell carrying 23 chromosomes,
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are going to undergo pro fes meta phase and a
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face to face.
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The chromosomes will line up in the middle.
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Chromatic DS will separate on.
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They will result with four cells.
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So this is my horses to pro face to Meta
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Phase two and phase two and telephones too.
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And again, if you look at this events, you'll remember
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my tonsils.
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The difference between uses one and two is very clear
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where during meta Phase one in Moses, one chromosomes line
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up as birth on a nanophase.
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One chroma.
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Chromosomes separate.
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Where else in New York says toe chromosomes lined up
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beside each other on cremated separate.
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So the number of chromosomes and pro phase to its
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A three and interface to onside.
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The kindness is the number will remain three.
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In this example.
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In our body, it's going to be 23.
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So is one reduction of division.
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It reduces the number of chromosomes.
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It keeps the number as it is, but it will
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for four cells, each cell having single cremated or 23
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single car models.
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As a result, I'm having four help Lloyd cells with
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23 number off chromosomes, each chromosome a single cremated.
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Now this a gruff explains the content off DNA, Third
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Division or per Moses.
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If you look at this graph way can see 12354
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and five, we can see three different values for DNA
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number one, it's the content or the amount of the
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A N G one before the is copied.
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Two is the content of the A After us phase
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during interface when the when the DNA is copied.
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So we have doubled the amount of DNA.
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Three. It's the first division when when Moses one splits.
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This information the chromosomes into two cells on dhe during
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55 Actually, it's me also is to when sister promoted
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separate during your sister.
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So if I start with a number off our number
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of chromosomes and one, I will end up having half
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off it.
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And four, It means if I have 46 I would
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have 23.
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Now, this is the graph form uses.
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The graph for my sources will be different because my
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sources will end up having the same amount, same content
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off DNA at the beginning and at the end of
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the division.
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So in this model we can see the different phases
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off different places off on each phase.
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It has its obvious events happening in each one off
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these faces.
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At the end, we are forming here for for cells
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that are employed, each self having half number of chromosomes.
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It means 23 chromosomes okay again says it's the cell
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division that occurs on commits or sex sells.
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It will result in the reduction of the number of
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chromosomes. It will result in genetic variation due to crossing
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over and do toe independent assortment.
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Without Moses, the continuation off species won't be able to
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happen because to maintain the number of chromosomes and a
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species the spur must carry.
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Have the number of chromosomes on the egg must carry
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Have the number of chromosomes.
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In addition to that, these cells that are produced the
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sperm or that they will carry each time different information,
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different genetic makeup.
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That's it for me.
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AOSIS. Thank you for watching.