This content explains chromosomal mutations, which involve changes to entire chromosomes, differentiating them from point mutations. It details structural and numerical types of chromosomal mutations, their subtypes, associated disorders, and phenotypic effects, particularly in plants.
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will talk about chromosome mutation and
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a chromosomal mutation is any change
that occurs within the chromosome
unlike point mutations that alter a gene
or a segment of DNA in the chromosome
chromosomal mutations change the entire chromosome
chromosome
so we have seen in our previous lecture
that point mutation Alters a single base
but chromosomal mutation Alters a chunk
of DNA includes many bases hence affects
Let's see different types of chromosomal mutation
mutation
first is structural and second is
numerical mutation
let's talk about structural mutation first
first
this type of mutation Alters the
structure of a chromosome
and there are different types of
structural mutation
such as deletion duplication inversion
and translocation
so we will talk about them one by one
first is deletion
this type of mutation causes the loss of
a part of a chromosome
let's see the figure here
so this is the chromosome and this part
is deleted from this chromosome and the
new chromosome doesn't have this part okay
so common disorders due to deletion
mutation in humans are
cry to chat cystic fibrosis Etc
Etc
next is duplication
in this type of mutation a part of a
chromosome is present in excess of the
normal composition
let's see the figure
so this is the normal chromosome and
this part is duplicated like these and
the new chromosome contains
okay
uh a common disorder due to human
duplication mutation is
next is inversion
during inversion a portion of the
chromosome is reversed and gets inserted
back into the chromosome
there are two types of inversion exist
pericentric and paracentric
pericentric inversion
during a pericentric inversion the
inversion involves the centromere of the chromosome
chromosome
and paracentric inversion so during a
paracentric inversion the inversion does
not involve the centromere of the chromosome
chromosome
let's see the figure here
so this is pericentric inversion
so this part is reversed in this
and it includes the centromere part
if you see paracentric inversion you can
see that this part that is getting
a common disorder due to inversion
mutation in humans is hemophilia a
next is translocation
translocation happens when a fragmented
chromosome joins with a non-homologous chromosome
chromosome
let's see the figure here okay
okay so
so
these two are non-homologous chromosomes
both the chromosomes are broken and
this part joins with this
and this part joins with this
like this
so this is an example of reciprocal translocation
common disorders due to human
translocation mutation are infertility
and cancer okay
okay
so next we will talk about numerical mutation
mutation
this type of mutation Alters the number
of chromosome
there are two types of numerical mutation
mutation
aneoploidy and polyploidy
anuploidy aneuploidy is a type of
mutation that results in the loss or
gain of one or more chromosomes
so loss of a single chromosome is called
monozoamine we can represent monosomi as
2N minus 1. the example of monosomi is
Tana syndrome here One X chromosome is
missing in females that means females
next loss of a pair of chromosomes is
called nalisomy
we can represent Nali zombie as to n
minus 2. humans with this condition do
not survive
addition of a single chromosome is
called Trisomy we can represent rhizome
as 2N plus one example of Trisomy is
Down syndrome here one extra copy of
chromosome number 21 exists
so the people who have Down syndrome
addition of a pair of chromosomes is
called tetrazomy we can represent
tetrazomy as 2N plus 2. the example of
tetrazomer is tetrazomi X
here four copies of the X chromosomes
are present in females that means
females have total 48 chromosomes
next we will talk about polyploidy
polyploidy is a type of mutation that
occurs when an individual Bears more
than one haploid set of chromosomes
so we have two sets of chromosomes and
we are called diploid
if the individual beers three sets of
haploid chromosomes the condition is
called triploid
if the individual beers four sets of
haploid chromosomes the condition is
there are two types of polyploidy first
is auto polyploidy and second is allopolyploid
allopolyploid autopolyploid
autopolyploid
so Auto polyploids consist of the same
basic set of chromosomes but multiplied
to form multiple cells
so what does that mean
okay so we have 46
chromosomes
in each cell so we can say that 2N
is equal to 46.
46.
that means n is equal to 2nd 3. that
means we have two sets of chromosomes
suppose all 23 chromosomes get duplicated
duplicated
so how many chromosomes are there in our
cell after duplication
that is
40 6 plus
23 that is 69.
that means now we have three sets of chromosomes
right this is called Auto triploidy we
can represent it as
3 n or
or AAA
AAA
suppose again all 23 chromosomes get multiplied
multiplied
so now we have
69 Plus 23
23
is equal to 92 chromosomes that means
now we have
four sets of chromosomes
chromosomes
this is called Auto tetraploidy we can
represent it as
4 n or
capital a capital a capital a capital a okay
okay
next is allopolyploid
allopolyploid
allopolyploids are the polyploids that
result from the doubling of chromosome
number in a hybrid from two different species
species
so we will understand these from this figure
figure okay
okay
so this is species a which contains
total four chromosomes that means 2N is
equal to 4.
this is species B which contains total
six chromosomes
that means 2N is equal to 6.
both pieces generate gametes
and we know that gametes get generated
after meiosis and number of chromosomes
become half
but here due to an error gametes are not
haploid there is no reduction in
chromosome number
and due to the fusion of these faulty
gametes are hybrid forms
which contains total 10 chromosomes
that means 2N is equal to 10. this type
okay
so polyploidy is a common phenomena
among plants
polyploidy can be observed in dope grass
that is cyanodon dactylon which is
cultivated in South Asia it is triploid
and sterile but can be propagated vegetatively
vegetatively
animals rarely exhibit polyploidy but
leeches flat worms and Fishes too
let's see some phenotypic effects of polyploidy
polyploidy
in Plants the most common morphological
effect of polyploid is giantism that is
seen in large sized pollen and cells
polyploidy reduces the rate of cell
division and thus the plant growth rate
also decreases
polyploidy leads to reduced auxin
content which decreases their rate of respiration
respiration
polyploidy also reduces the fertility of plants
plants
so this is all about today's lecture I
hope you liked the lecture if you want
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