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section 9.4 addresses what occurs during the eukaryotic cell cycle the eukaryotic
cell cycle consists of interphase followed by cell division interphase is
a time of acquisition for nutrients growth and chromosome duplication during
cell division one copy of every chromosome and exactly one half of the
cytoplasm and organelles are parceled out into the two daughter cells cells
spend about ten percent of their time in the actual divisional processes ninety
percent of their time in the interphase period which is a preparation stage so I
put here a good link for a mitosis video again you can click on this I'm not
gonna take the time to play it here but I would encourage you to take a look at
that it's a pretty good YouTube video that talks about mitosis during
interphase most eukaryotic cells spend about 90% or the majority of their time
in this interphase period interphase is divided into 3 sub phases G 1 which is
the first growth phase or the first gap phase this is a time for the acquisition
of nutrients and for the cell to grow to the proper size during the S phase which
stands for synthesis this is characterized by DNA being duplicated
and every chromosome is duplicated during this phase during g2 the second
growth or second gap this includes a completion of the cell growth and
preparation for the division of the cell into the daughter cells there are
actually many checkpoints that are built into interphase to regulate whether a
cell should duplicate or not now these checkpoints we'll talk about a little
bit later on at the end of this chapter but essentially the bottom line is you
don't want to go through three-quarters of the prep stages and realize that you
don't have enough nutrients or enough materials to complete the process so
that's why these checkpoints play a very important role to make sure everything
is in line everything's been copied correctly
before you actually proceed through the divisional stage
here is a picture that illustrates the different phases that we see taking
place again 90% of the time is the interphase period
which would be the yellow wedge interface is divided up into g1 s and g2
and then the actual divisional stage would be prophase metaphase anaphase
telophase and cytokinesis so you may have heard the term p mat PMAT that
stands for prophase metaphase anaphase and telophase oh this is actually this
is a duplicate so don't worry about this we just looked at this before mitotic
cell division involves two distinct steps during mitosis we have nucular
division whereby the nucleus of the cell and the chromosomes divide each daughter
cell or each daughter nucleus receives one copy of each of the replicated
chromosomes from the parental so during cytokinesis which is the cytoplasmic
division the cytoplasm is divided roughly equally into the two resulting
daughter cells mitotic cell division takes place in all types of eukaryotic
organisms it's the mechanism for asexual reproduction mitosis followed by
differentiation of the daughter cells allows for a fertilized egg to grow into
an adult what that statement means is again you have *** fertilizing egg
forms a zygote that zygote then goes through multiple divisions where one
cell turns into 2 to 4 to 8 to 16 to 32 it increases the number of cells that
dividing one to two to four to eight to sixteen is through mitosis mitotic cell
division also allows organisms to maintain repair and even regenerate body
parts it's also the mechanism by which stem cells reproduce and humans have
about 75 or scuse me between 50 to 75 trillion cells
now where would that number or the difference between 50 and 75 come into
play think about an infant much much smaller than a mature adult so younger
people that haven't accumulated as much mass would be closer to the 50 whereas
mature adults close for the 75 trillion mitotic cell division on the other hand
or meiosis occurs in animal ovaries and *** and is the prerequisite for
*** reproduction in all eukaryotic organisms so meiosis involves a
specialized nuclear division called meiosis and two rounds of cytokinesis 2
divisional steps end up producing 4 daughter cells that can then become
gametes these daughter cells are genetically different from the parental
cell and also different from one another and each daughter cell is now haploid it
has exactly one half the genetic information as the parental cell which
was diploid so gametes *** and egg they only have one number chromosome
number one one chromosome number two one number three one number four one number
five and so on and so on so if you want a great meiosis video again click on the
link right here