Hello guys how are you doing? In this visual lecture we will talk about what is Ploidy
number? What is euploidy? what is and aneuploidy? what is polyploidy? and all these related
confusing terminology and we will learn all these things in a very logical Fashion. So
let's start the lecture hello I am Dr Aizaz from medicovisual.com welcome to this visual
lecture. [Music] Starting from very basic concept that what is the ploidy number? Ploidy
means how many sets or how many times something is present? How many turns of something is
present? Ploidy means how many, how many sets of chromosomes are present. You know in human
cells, in human somatic cells, I am not talking about gametes, in human somatic cells we have
how many sets of chromosomes normally present? Two sets, so ploidy number of human somatic
cell is 2 and 2 yes 2n this ploidy number is denoted by, demarcated by n so we will
see, we can say this 2n then there is a similar or related term to this that is called Euploid.
Eu means true ploid means how many times how many times something is present. Right, so
Euploid chromosome number is said to be euploid when it’s, when this number is multiple
of n. Let me, let's make it more clear. For Example, one of the type of Euploidy Or Euploid
is monoploidy but mono, mono means one so what monopoly means that we are having one
set of chromosomes so 23 multiplied by one again it is a multiple of n so here 23 is
n and 23 multiplied by n is 23 so if a cell is having 23 chromosomes in the form of one
set of chromosomes then we will call it Monoploid that cell is monoploid cell. Right, and the
ploidy number of that cell will be one n. Similarly, an example of that is: Yes, gametes.
Let’s suppose sperm it is having a single set of 23 chromosome here this is and let's
suppose an ovum and it is having single set of 23 chromosomes 23 multiply by one so gametes
are Monoploid. Now you will say gametes are haploid. I will tell you what is the difference
Between them. Don’t worry. Similarly, there is a term called diploid or diploid Diploid
means again we are having, di means two, we are having two sets of 23 chromosomes so 23
multiply by 2 is 46 again this 46, this chromosome number 46 it is multiple of n n is 23 so if
we multiply 23 by 2 it will become 46 again it is multiple of n so diploid is a type of
euploid and its n number is 2n example of that is Somatic cell this is representation
of zygote and from zygote onwards the complete Organism, the complete human that will be
formed all of that human cell will be Diploid and these diploid cells their n number will
be 2n. So, these are two related concepts. But you should not confuse these two Terms.
They are different terms but they are very related to each other. Then there is triploid
that is there its n number is 3 and 23 multiplied by n clear example of that related to humans
is that let's suppose normally what happens that this is a an ovum and it is fertilized
by a normally by a single sperm only but sometimes really more than one sperm let's suppose two
sperm may fertilize it then this sperm will be this sperm will be containing 23 chromosome
this will also be containing 23 and 23 chromosomes will be of this ovum so 23 multiplied by 1
2 and 3 so there will be triploidy here. Right, and then there could be tetraploidy Pentaploidy,
hexaploidy and so on. Anything beyond diploid, anything beyond diploid is also called Polyploid.
Now, let me tell you something Interesting. Some organism, other than human, for Example,
some plants, some fishes and some plants for example banana their cells, they may be normally
Polyploid. Normally, humans and most of the organisms are diploid but some organism may
normally be polyploid. right, they may be for Example: tetraploid for example some species
of wheat they are normally hexaploid. Right, so that is something normal for some organism
but if a human is polyploid that is not normal that is an abnormality and we will discuss
later about chromosomal abrasions. Now what is haploid? Haploid simply means half of ploidy
number of somatic cells. whatever the chromosome number of somatic cell is if we divide that
chromosome number by 2 that is called haploid. For example, here we are having 46 chromosomes
in this somatic cell we are having 46 chromosomes if we divide this 46 by 2 the number that
will come is 23 and that 23 is Haploid so normally human gametes are Haploid. Right,
human gametes are normally Haploid and they are also monoploid. Now let's suppose an organism
not human any other organism if that organism’s somatic cells normally are tetraploid, right,
it's somatic cells they are normally let's suppose tetraploid then their haploid is not
monoploid then their haploid will be half of tetraploid that is their haploid will be
diploid. So, for human monoploid, for human and many other organisms Monoploid and haploid
means the same but actual meaning of these two terms are slightly different. So, you
must have clear and logical sense of these terms. Now let's talk about numerical chromosomal
abnormalities or numerical chromosomal Abrasions. We will try to classify them Logically so
it will be very easy for you to understand. Numerical chromosomal abrasions can be of
two types it could be a euploid abnormality in which the chromosome number is a multiple
of n. Now you may be confused here that how Euploid maybe an abnormality let me tell you
although the chromosome number is multiple of n but somatic cell is not diploid you know
normally human somatic cells must be diploid so if human somatic cell is something other
than diploid their chromosome number is not a diploid but still a multiple of n then that
is euploid type of chromosomal Abnormality. For example: polyploidy as I have already
discussed that two sperm or maybe three sperm they may fertilize a single ovum that may
lead to triploid and tetraploid and both of these are actually, polyploid situation What
about oligoploid? Oligoploid means that somatic cell is not diploid but it is less than diploid
it is still multiple of n but less than diploid. It, it means it may be monopoloid. My friends
there is no monopoloid situation in humans. Human body can not tolerate monopoloid situation.
Right, you cannot tolerate monopoloid situation it needs two sets of chromosomes to function
properly so, there is no oligoploid at least in human as far I know. Maybe there may be
some oligoploid situation in other organism I’m not sure about that But in humans that
is not possible. so Euploid abnormality and the other type of Abnormality is aneuploid.
An means not, abnormal or not and euploid means multiple of n so aneuploid means chromosome
number is not a multiple of n here it was a multiple of n but here it is not a multiple
of n and example of this is that normally 23 for humans 23 is the n number so it should
be multiple of 23 that is 46 or 69 for example but if it is not that it is less than diploid
or more than diploid for example Hypodiploid for example Monosomy, one chromosome is less
normally it should be 46 if one chromosome is less that will be not 46 but 45 for example
monosomy of any of the chromosomes we have discussed these things in a previous lecture
so rather than 46 45 so it is having 45 chromosomes here so that is 45 is not multiple of 23 23
multiplied by 2 is 46 not 45 so it is not multiple of 46, 23 other situation is hyperdiploid
for example trisomy, Right, there is extra chromosome and chromosome number is 47 and
again 47 is not a multiple of 23 or there may be Tetrasomy there is an extra chromosome
here and pentasomy and so on so monosomy could be of autosomal chromosomes monosomy only
but body cannot tolerate the monosomy of autosomal chromosomes so actually there is no example
of autosomal chromosome monosomy but what we can somehow tolerate the sex chromosomes
monosomy and example of that is Turner syndrome. Normally with this x there should be either
a y chromosome or another x chromosome if there was double x chromosome that would be
a normal female or if x y then that would be a normal Male but with x there is no extra
chromosome in this case so that is, that is called turner syndrome and that is sex chromosome
monosomy and then regarding trisomy again it could be autosomal chromosomes trisomy
and sex chromosomes trisomy there could be autosomal chromosomes Trisomy and three of
the common examples are Patau syndrome in which chromosome 13 trisomy is there and then
Edward syndrome chromosome number 18 trisomy and Down down syndrome and of course all of
these will be having 47 chromosomes an extra chromosome and then sex chromosome trisomy
is that there is one extra x chromosome that is Klinefelter syndrome. Now how can you remember
that which chromosomes trisomy is there but I have a nice mnemonic for you. First let
me tell you, you have to learn these numbers 13 18 and 21 and the good news is that it
is very easy to remember these numbers because in the life of human these number as a years
of age these are very important you know 13 years is the age of puberty 18 year is the
age of maturity or adulthood and in some countries 21 is the age of Adulthood. Right, so these
numbers are easy to remember. Now let me tell you how a baby or a child a young child will,
will pronounce these terms what about Edward syndrome he or she will say it like that “adualt
syndrome” it sounds like adult edward sounds like adults so chromosome number 18 edward
adult 18, 18 and what about down syndrome how a baby will pronounce down syndrome it's
like that Twone Syndrome. It sounds like 2 1. Down Twone 2 1. And for Patau syndrome
that is very easy p for patau syndrome p for puberty and the age of puberty is 13 years
often. Right, and what about Klinefelter I think it like this it is feminine father syndrome,
kline Feminine, kline feminine and Felter, father. Actually, these are the names of scientists
and I am sorry to those scientists that I am making fun of their name but that is just
to make you remember these Right, so feminine father you can remember that this father is
having one extra x Chromosome. actually, here is the mistake in this slide it is double
x y clear? the feminine father it is father because it is having y chromosome actually
these , they are usually non fertile so just for the sake of remembering that there is
Y chromosome here and feminine because there is one extra girlish or feminine chromosome
one extra x chromosome rather than x y there is double x y here and Turner syndrome I do
not have any mnemonic but you can just remember that in terms of syndrome there is monosomy
of x chromosome. so, there is one less X chromosome. So, let me tell you something interesting
normally females have two x chromosomes and out of these two x chromosomes, one of the
x chromosome is randomly inactivated it is randomly converted into you can see a crumpled
ball it is super Condensed, it is super quiet super compressed and it is inactivated permanently
and this inactivated x chromosome is called bar body and this process of conversion of
x chromosome into bar body is also called Lionization. Right, I will not discuss the
details of lionization but that's it that's how it is so we are having bar body here so
this is what happens in a normal cell but in Turner syndrome there is a single x chromosome
and no bar body no other x chromosome that could be turned into bar body. Now, the interesting
question here is that the body when it gets when the female cells when it gets two chromosomes
one of one of the x chromosomes it actually one of the x chromosome it inactivates anyway
but when it is not getting any of the Extra x chromosome the body is angry and this leads
to Turner syndrome. Why so? That is, it is confusing Well, the answer is very simple
this bar body that is formed actually all of these genes are not totally inactivated
some of these genes from these, from this bar body they are still active and these are
expressed normally. Some of these genes, they are normally expressed and when this bar body
is lost here those genes that are normally expressed they will be lost. right, they will
be lost and that leads to the symptomatology, the complex of symptomatology that we call
Turner Syndrome. So, this was about aneuploidy and all these related terms. Thank you so
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