Behaviour of Chromosomes during meiosis Video Lecture - NEET

hello friends this video on principles
of inheritance part 22 is brought to you
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now we will talk about the behavior of
pros on stealing meiosis we are more
interested in my office because meiosis
is the type of cell division which is
involved in the process of gamete
formation and gamete formation plays an
important role in the process of
maintenance because clearly this is
something which is related to sexual
reproduction and in sexual reproduction
gamete formation is the process by which
it is initiated so - escape a major
hotel so let us quickly see what
happened during meiosis and how the
Cozens underwent a change during meiosis
so meiosis it is a specialized type of
cell division which reduces the
chromosome number by half and that is
why it is also known as the reduction in
division so when I say chromosome number
is reduced by half what I mean is if you
start with a diploid cell you can end up
getting employed cells so that is how
your frozen number gets reduced so
diploid cells will have some sets of
chromosomes and from that you end up
getting haploid cells with one set of
chromosomes
this occurs during Gabby kitchen s is in
plants and animal cells now by meiosis
occurs during garbage witnesses because
the gametes is a process of grabbing a
genesis what happens gametes are being
formed and gametes are haploid cells so
basically we want to form haploid cells
so we need meiosis
so in case of human beings also the
gametes others form and the over so they
are all haploid cells to inaudible whose
then produced insects meiosis has to
want even in Mendel's experiments we saw
all right how having formation occurs so
for that information in these meiosis
now the process of meiosis involves two
sequential cycles and they are meiosis
one and my office's truth so the meiosis
one is the reduction and division where
the actual decrease in the chromosome
number take place so as a at the end of
meiosis
you're applying cells are produced from
one diploid cell so you start the
process with one diploid cell after
meiosis one you are left with two
haploid cells after meiosis two you are
at with four haploid cells so basically
from once deploying cell you are able to
produce four haploid cells meiosis two
is almost like an equation and division
I mean it is almost similar to mitosis
because my process is an equation on
diffusion where the chromosome number
remains the same so meiosis one will
reduce the number of chromosome to half
and meiosis 2 will divide it further so
you will get four haploid cells from
diploid cell so that is what you will
get if you have one diploid cell at the
end of meiosis one and meiosis two you
will get four haploid cells so let us
look at the overall process of my
officers this is how the overall process
looks like so if you see this entire
part else minus one so this is meiosis
one and this entire part is meiosis two
so each my houses in turn is me is has
four stages that is prophase metaphase
anaphase and telophase now I will not
get into length detail of my officers if
you want to learn it in detail you can
refer the list on cell cycle or class 11
there I have discussed mitosis in detail
however I will complete review so that
at least for now you are able to
understand the next concepts which we
are going to talk about in progress over
three of inheritance so this process
basically starts with prophase one and
improve this one what do you see a lot
of phases significant changes take place
during prophase one so if you say it is
important when the homologous
chromosomes become visible again you can
see this is one chromosome this is
random chromosome so these two are the
two homologous chromosome you can I hope
you can see this is fun this one's one
again this is not one so you have one
set of homologous chromosome again me
and you have quite set of formula
co-sponsors and the homologous
chromosome start getting visible
selecting
try to write it here that'll make things
easy so what happens to link hopefully
is one
so initially how was the volume is 4 so
this is how the rumor goes promos of
your plans these to our locus for ozone
then what will happen the whole Lucas
promo zone will it replicates and under
the rose only creates two for the system
from Athens so now you have duplicated
over Lucas chromosomes somewhat like
this okay in this prophase one it all it
is also seen that the homologous
chromosomes start together now what do I
mean when I say they start pair you up
so this is one homologous chromosome and
this is another homologous chromosome
like if you see they have started
pairing up and this is very very
important so these sites at which they
start connecting with each other or they
start getting linked to each other these
are known as the science of crossing
over what happens at the science of
crossing over they actually change the
small part of each other that is what
happens as a design doctors crossing
over at these two regions they have one
crossing over and these two regions
there some part of the the first rows of
get exchanged with the second chromosome
and some part of the second chromosome
gets exchanged with the first chromosome
and this process is known as
recombination so towards the end of
prophase 1 what happens is the first
formal lose form ozone loops somewhere
like this so if you see the corner most
portion have got X exchanged and the
second envelope will form ozone loose
somewhat like this so if you see here
the entire chromosomes mind but these
portions which are never crossing over
they exchanged some some of their parts
so as a result what happened
so you basically now have two over locus
chromosomes but
of their fax and pin exchange now what
happens if a part of the chromosome has
got exchanged the chromosome contains
gene so that means the gene which was
present in this part but extinct this
part and the gene which was present in
this part work exchanged with this part
so basically the genetic material is
getting mixed up there is some blending
which is happening inside between the
mother MacLennan
trade cycle paternal traits so it is
quite possible that let us suppose the
gene for hair color and was present here
and that gene for hair color went here
and it got somehow it got blended or
mixed up so you might find new trains
due to cross over right so I am NOT
getting into the details and how it is
one when it is one for that event and
for those videos but just try to
understand this that when crossing over
takes place basically what happens is
that some of the trails this is some
wrinkling or some mixing up of some
portion of the chromosome and every
portion of the chromosome contains some
genes and those genes then tone some
traits that is why in a child there
might be some new characters which are
not exactly present in the same way in
any of his parents and this happens due
to crossover right so this is one
important thing which change is here and
this is going to be one important point
when we talk about the chromosomal
theory of inheritance so this is how
protozoan plays a very important role
now what happens in the next stage that
is the metaphase in later phase
microtubules start to forms relevancy a
network being form that is for the
spindle fiber network so these
microtubules gradually tend to form the
spindle network and as a result all the
over locus chromosomes are aligned at
the equatorial plane the outer layer
lying and equatorial plane if they are
aligned due to the continuous forces
which are next exerted on these two
tracks by the five spindle fibers so the
spindle fibers attached to the
homologous chromosome here you can see
the
25 us and attached it and they all
aligned at the equator of the metaphase
and this is known as the formation of
the metaphase plate so this is what make
up a straight because a plate length
structure is formed along the equator at
this stage now what happens in anaphase
1 so in the next phase the oval Ubu
scores or separate once they get aligned
at the equator then what happens this
spindle fiber tend to push it this side
this tend to push it this side so both
are separated away from each other
solder but still the sister chromatids
are still attached to it you see so
wonderful whose clothes on whose the
sign the other homologous chromosome
also moves this side and on the other
side you have again a pair of homologous
chromosomes right and if you also see
that fear not both the same set of
homologous chromosomes are going to one
side so one blue is going to side and
one red is going to side similarly one
who is going to the side one red is
coming this side so basically when the
stand will divide so each cell will have
combination it will have one set of
chromosomes from one guru who's there it
will have madness of chromosome from the
other pair okay and sister providers are
still attached he'll see these are the
sister chromatids they are still
attached so at the end of anaphase 2
enough is one what happens tel aviv's 1
starts and what happens in telophase 1
so in telophase 1 cytokinesis stats
telophase cytokinesis and what is the
meaning of cytokinesis it means division
of the cytoplasm so the cytoplasm will
start to divide when this once the
cytoplasm divides it will start
developing the plasma membrane and the
proper two different cells will reform
so two daughter cells are formed with
half number of chromosomes so if you see
the initials and how many chromosomes it
had if you see here it had this is one
pair of all of the screws on this is one
pair
Roma's alright so it had two pairs of
homologous chromosomes right now it just
has one pair of chromosomes so the
growers own number has reduced to half
so you received two daughter cells
daughter cells and these daughter cells
are haploid right so haploid cells are
born at the end of meiosis one now what
happens to each of these cells on each
of these a haploid cell will undergo
meiosis two what happens in meiosis one
- it is is similar to my process so
basically here again spindle formation
will take place in the prophase 2 so the
chromosomes become contact and spindle
formation start to begin
now once the spindle again attaches
itself to the centromere of the sister
chromatids and then begin the spindle
and again the sister chromosomes will
align themselves at the metaphase at the
equator only and if we form the medical
space dependence - and again due to the
force exerted on both the ends the
sister chromatids will separate them so
in anaphase 2 what will happen the
sister chromatids will separate your
sister for my teens will separate and as
a desire you will be left with four
haploid cells so answer design for
haploid cells with before so basically
here in this case the sister chromatids
were still there so this was just two
copies of the same chromosome something
of that sort
now they also got separated but you can
still see the u2 recombinations
inclusion or exchanged red so these are
the portion of which what explains and
these portions will actually give rise
to some new trains and up offspring so
here in this phase if you look at the
anaphase 2 you can actually relate it to
the principle of segregation where for
gamete formation the animals tend to
segregate so that is what is happening
even here
also right so as you see the end result
is that you started with one diploid
cell and you ended up with four haploid
cells and during this process the thing
that means my house is very much
different from my process is them
changes which take place during prophase
one that is crossing over recombination
so these are the changes which make my
meiosis very much different and as a
result of which the cells which are
produced as a result of meiosis they are
not exact identical groups of their
parents this work they show some new
traits they also show some differences
from their parents and all that is
because of the process of crossing over
which take place during prophase one now
looking at the similarities between the
behavior of chromosomes and the behavior
of the maintenance factors and including
Curie came up now this theory doesn't
come about so there were quite a few
scientists who started working on a man
who started progress the work further on
genetics so they kept on performing more
and more experiments they tried to now
sense cell division was properly
feasible now so they try it started
understanding the behavior of rows homes
how to they behaved and then they found
that wonderful laws were given by mental
the behavior of the factors were quite
similar to the behavior of the
chromosomes so now they started to
connect the dots they wanted to develop
what they want they want you to connect
the link between the factors that is
when alien factors and chromosomes and
that is how they came up with the
chromosomal theory of inheritance thank
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