Meiosis Stages Video Lecture - Biology Class 11 - NEET

hello friends this video on cell cycle
and cell division part 10 is brought to
you by exam fee or Farm no more feel
from exam so we will now talk about the
next type of cell division that is
meiosis now some of the people pronounce
it as meiosis or meiosis whatever you
call it now there might be some
questions in your mind when you think of
sexual reproduction what do we need for
sexual reproduction we need the sex
sense that is the gametes so gametes are
required for sexual reproduction we all
know that we also know that gametes are
haploid cells that is they have just one
set of chromosomes now the question is
when we talked about mitosis we say that
mitosis are person all the diploid
somatic cells of animals but animals
have employed sex sets so from where do
these sections come so how are these
gametes formed now gametes are formed
from diploid cells how because gametes
are employed and you know all of their
body cells are diploid so if gametes are
formed from some of the cells that means
it is formed from diploid cell now the
question is how is applauding cells
spawn from diploid cells so that is the
question because mitosis doesn't ensure
that conversion so for that meiosis came
into picture so what is meiosis it is a
specialized type of cell division which
reduces the chromosome number by half so
if before division the chromosome number
was 2n so after division it becomes n so
that means diploid cells can get
converted into haploid cells so this is
the main difference between mitosis and
meiosis in mitosis the chromosome number
is conserved
that is a
chromosome number was doing it will be
doing but here it becomes half so here
the parent cell is deployed whereas the
daughter cells are haploid and this is
how the female by male and female
gametes are produced in animals so if
you have a parent cell which is deployed
it forms for daughter cells which are
all haploid so these are only applied
with this pins diploid
so there are two differences in mitosis
the daughter cells were all deployed
here the daughter cells not applied
there two daughter cells were formed
from one parent cell and here for
daughter cells are formed from one
parent cell so these are some of the
differences between meiosis and mitosis
it occurs during gamete oogenesis in
plant and animal cells what does
gametogenesis the process of formation
of gametes gametes are nothing but the
sex cells so when you talk about sex
cells in human beings we are talking
about the sperm which is the males Excel
and the ovum which is the females Excel
it is to get some of the important
features of meiosis pairing and
recombination of homologous chromosomes
now in case of mind ourselves what was
the basic constant replicate and divide
so copying of their hands and dividing
the DNA into daughter cells here the key
concept is pairing and recombination so
what do we mean by pairing and
recombinations are here first what will
happen now since you have to separate
gametes so the male will mail your sex
cell will contribute something female
sex cell will contribute something anti
pairing between the two will happen and
recombination that means sharing some
part of the male will get exchange to
the female some part of the female will
get exchange to the male so that means
recombination can happen now we will
understand
sparing and recombination in even
morning so what happens is let us
suppose this is your parent cell now
this has chromosomes like this and I
suppose this chromosome is obtained from
the father and this chromosome is
obtained from the mother so what happens
this will finally give rise to four
haploid cells so four haploid daughter
cells will be formed as a result of
meiosis no when you look at the daughter
cells you will say they are somewhat
like this so if you look at it you see
that they are all like mixed none of
then he only resembles the father
none of them purely resembles the mother
so if you see in all of them one of the
same is one of the chromosome is like
the father or the mother that is it is
either white or it is red so this is
your white and this is these are your
rates but here you see recombination is
occurred so in one chromosome you have
both the traits that is the mixture of
the traits and that is why none of the
daughter cells is exact copy of parent
set this is very very important here now
just to take an example of human beings
now take example of each one of us
people often say that you look very with
similar to your dad or I look very
similar to my mom so we get such
comments and we often see such
similarities but that doesn't mean that
we look exactly similar to ours however
that happens only certain exceptional
cases but otherwise there are some other
other differences and you can
easily distinguish between a father and
the son even though there are a few
similarities that is because that son
has some traits of his father some
traits of his mother and some new traits
which has come as a result of
recombination because the traits have
got combined from who the patterns and
he is altogether got a new trade
so that is why none of the daughter
cells produced in case of meiosis is
exactly similar to the parent cell so
that is why we see pairing and
recombination so here also pairing is
taking place
they are pairing up together the
chromosomes are fair enough but
recombination so the trades are getting
combined now there is the villain to
mitosis meiosis is also divided into
several stages so what are those
different stages now broadly meiosis is
divided into two cycles that is meiosis
one and meiosis two now why do we have
two cycles in meiosis because in meiosis
the chromosomes gets reduced so you
start with a diploid cell it gives four
haploid so in the first cycle of meiosis
it will give two applied cells and in
the second cycle of meiosis it will
again those two will give rise to four
haploid cells so the final will be four
applied sense so that means it is
divided into two phases that is meiosis
one and meiosis two there each of these
meiosis 1 and meiosis 2 will have the
subsequent stages within them so when
you talk about the cell cycle that is
the life cycle of a cell so from where
does the meiosis starts we also starts
exactly after the synthesis field so
first will be the first gap fields this
will be their synthesis phase will also
be there when the DNA will be replicated
or when the DNA will duplicate itself
and after this S phase what will happen
it will not enter into g2 phase it will
not get into the gap
instead it will get into meiosis 1 so
the first Moo your system after this it
will get into meiosis 2 that is the
second phase of meiosis now as a result
of meiosis 1 and meiosis 2 what will be
the result what will be formed Hepler
extends will be formed as I said four
haploid daughter cells will be formed
she applied cells are formed now what
will these haploid cells to most of
these employed cells are basically the
gametes the male and female gametes so
they will undergo fertilization right
the male gamete and the female gamete
fertilize or fuse together to form a
zygote which is again deployed so after
fertilization this will again form
diploid cells and then what will happen
to these diploid cells these diploid
cells will again get into g1 that means
that diploid cells once they are formed
they are like any other somatic cells of
the body
so these diploid cells will undergo the
metabolic processes if they will grow
they will become mature so they are
basically in the g1 phase gap one feels
after that again the synthesis phase
will come and then now they are diploid
cells therefore after this synthesis
phase they can either go to mitotic
cycle through the process of mitosis or
they can go through meiosis so that is
their choice so - might talk mitosis and
meiosis they are related to each other
because meiosis forms the haploid cells
which fertilized later to form diploid
cells and the diploid cells again
undergo multiple division to form more
and more diploid cells so that is how
mitosis and we
I related by they both do not fall in
the same cycle so meiosis is like after
the S phase after S phase either it will
go through g2 and then my Datuk phase or
it will go directly to meiosis phase so
I hope this is clear that we're exactly
in the life cycle of a cell mitosis and
meiosis crimson so now we will see what
are the different stages involved in
each of these cycles so let us talk
about meiosis 1 meiosis 1 will have four
stages again the name of the stages are
very similar to what we have studied in
mitosis so it will have prophase 1
metaphase 1 anaphase 1 and telophase 1
so these are the four stages of meiosis
1 similarly meiosis 2 will again have
steps like prophase 2 metaphase to
anaphase 2 and telophase 2 so what we
are going to do is we are going to talk
about each of these steps in detail and
we will see how the entire process of
cell division or meiosis will take place
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