●The `color{Violet}"chromosomal disorders"` on the other hand are caused due to `color{Violet}"absence or excess"` or `color{Violet}"abnormal arrangement"` of one or more chromosomes.

● `color{Violet}"Failure of segregation"` of chromatids during cell division cycle results in the `color{Violet}"gain or loss"` of a chromosome(s), called `color{Violet}"Aneuploidy"`.

● For example, `color{Violet}"Down’s syndrome"` results in the gain of extra copy of `color{Violet}"chromosome 21"`.

● Similarly, `color{Violet}"Turner’s syndrome"` results due to loss of an `color{Violet}"X chromosome"` in human females.

● `color{Violet}"Failure of cytokinesis"` after telophase stage of cell division results in an increase in a `color{Violet}"whole set of chromosomes"` in an organism and, this phenomenon is known as `color{Violet}"polyploidy"`.

● This condition is often seen in `color{Violet}"plants"`.

● The `color{Violet}"total number"` of chromosome of a normal human being is `color{Violet}"46 (23 pairs)"`.

● Out of these `color{Violet}""`22 pairs are autosomes and one pair of chromosomes are `color{Violet}"sex chromosome"`.

● Sometimes, though rarely, either an `color{Violet}"additional copy"` of a chromosome may be included in an individual or an individual may lack one of any one pair of chromosomes.

● These situations are known as `color{Violet}"trisomy or monosomy"` of a chromosome, respectively.

● Such a situation leads to very `color{Violet}"serious consequences"` in the individual.

● `color{Violet}"Down’s syndrome"`, `color{Violet}"Turner’s syndrome"`, `color{Violet}"Klinefelter’s syndrome"` are common examples of chromosomal disorders.

● The cause of this genetic disorder is the presence of an `color{Violet}"additional copy"` of the chromosome number 21 (`color{Violet}"trisomy of 21"`).

● This disorder was first described by `color{Violet}"Langdon Down"` (1866).

● The affected individual is `color{Violet}"short"`, `color{Violet}"statured"` with small round head, `color{Violet}"furrowed tongue"` and partially `color{Violet}"open mouth"`.

● Palm is broad with characteristic `color{Violet}"palm crease"`.

● `color{Violet}"Physical"`, `color{Violet}"psychomotor"` and `color{Violet}"mental"` development is retarded.

● This genetic disorder is also caused due to the presence of an `color{Violet}"additional copy of X-chromosome"` resulting into a karyotype of `color{Violet}"47, XXY"`.

● Such an individual has overall `color{Violet}"masculine development"`, however, the feminine development (development of breast, i.e., `color{Violet}"Gynaecomastia"`) is also expressed.

● Such individuals are `color{Violet}"sterile"`.

● Such a disorder is caused due to the `color{Violet}"absence"` of one of the `color{Violet}"X chromosomes"`, i.e., `color{Violet}"45 with X0"`.

● Such females are `color{Violet}"sterile"` as `color{Violet}"ovaries are rudimentary"` besides other features including lack of other `color{Violet}"secondary sexual characters"`.