In a living cell every activity and character are completely controlled by the genetic material present in a cell and it is present inside the nucleus in eukaryotes while in case of prokaryotes the genetic material present scattered in cytoplasm without any boundary of membrane.
During the cell division along with the division of other components genetic material is also distributed in daughter cells and during this division or after division any type of abnormalities in genetic material cause abnormal activities of a cell.
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What is Chromosomal Abnormalities:
In a cell any type of abnormalities in the number of chromosomes or any abnormalities in a single chromosome or more than one chromosome cause abnormalities in living organisms and the abnormalities can be different types which we will discuss below.
Aneuploidy:
In a cell, the number of chromosomes is fixed and during cell division the genetic material duplicates and the number of chromosomes is also fixed in daughter cells.
There are different types of mechanism to distribute the chromosome during cell division but when the cellular mechanisms fail to distribute the chromosome in dividing cell then uneven distribution of chromosome occurs which results abnormal number of chromosome in a cell, either one or more chromosome remain missing, or one or more chromosome remain extra and it is known as aneuploidy.
Polyploidy:
In a cell a fixed number of chromosomes is present but sometimes during cell division duplication of genetic material occurs but the cell fails to perform cytokinesis.
Fail in cytokinesis cause increase in the chromosome number in whole set of chromosome and it is observed most frequently in case of plant cell sometimes due to effect of some chemicals polyploidy occurs, for example colchicine is a chemical which prevents the formation of spindle fibres during cell division and cause fail in distribution of chromosome in a cell.
Some Examples of Chromosomal Abnormalities:
Turner Syndrome:
In a normal human number of chromosome in a diploid cell is 46 among which 22 are autosomes while 2 are allosome and in human male the two allosome are ‘X’ and ‘Y’ while in case of human female two allosome are ‘X’ and ‘X’.
Turner syndrome is a chromosome abnormalities when one ‘X’ chromosome in human female remain absent so total number of chromosome in this case become 45 which is represented as (22+ X0) and we know that the ‘X’ chromosome is responsible for female characteristics in human female so in this case females become sterile.
Due to absence of the one ‘X’ chromosome in human females the Turner syndrome causes reduced expression of most of the female secondary characters and their ovaries also become rudimentary.
Down Syndrome:
It is a chromosomal abnormality when 21 no chromosomes have an extra copy in the cell which results in three chromosomes in case of 21st chromosome and this condition known as Down syndrome as well as trisomy of 21 no chromosomes. Down syndrome shows abnormalities in physical and mental level, specially the person who has Down syndrome suffer from restarted mental health.
The person with chromosome no 21 have shortness in their physical structure and their tongues show abnormal furrow, mouth is partially open and the palm is broad as compared to other normal individuals.
Klinefelter Syndrome:
It is an example of chromosomal abnormalities where the number of chromosome is 47 due to an excess ‘X’ chromosome in human male so it cause (22 + XXY) conditions and we know that ‘X’ chromosome is responsible for female characters while the ‘Y’ chromosome are responsible for male character.
So the more number of ‘X’ chromosome cause female characters dominant in human male but along with male character also present due to the ‘Y’ chromosome, they have muscular body structure like male but they show some feminine character like development of breast and the person suffer from Klinefelter Syndrome are sterile.
Read More: Chromosomal Theory of Inheritance
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