Question

Conditions of a karyotype $2n+1$,$2n–1$ and $2n+2$, $2n–2$ are called:

• A. Allopolyploidy
• B. Monosomy
• C. Aneuploidy
• D. Polyploidy

Answer 1

The correct option is C Aneuploidy

Karyotype:

Karyotype represents the paired and ordered arrangement of an individual's collection of chromosomes.

Aneuploidy:

Aneuploidy is a condition characterised by deviation from the normal chromosome number (2n) in a cell nucleus occurring due to failure of segregation of chromatids at the time of cell division. A cell nucleus showing aneuploidy has more or less chromosome number.

Depending on the number of chromosomes added or lost from the existing chromosome condition, it is represented by the following karyotypes:

$\bullet$ Monosomy = 2n-1
$\bullet$ Nullisomy = 2n – 2
$\bullet$ Trisomy =2n + 1
$\bullet$ Tetrasomy = 2n+ 2

Polyploidy :

Polyploidy refers to the condition of possessing more than two complete sets of chromosomes in a cell nucleus. It can be represented as 3n, 4n etc.

Allopolyploidy :

Allopolyploid refers to the addition of a complete set of chromosomes in a cell nucleus from a different species.

Monosomy:

Monosomy is a type of aneuploidy which refers to the condition when a chromosome is missing from a pair of chromosomes. It is represented by 2n-1, where n is the number of chromosomes in a haploid cell.

Final answer :
a. Aneuploidy

Summary

Aneuploidy
Aneuploidy is a condition characterised by deviation from the normal chromosome number (2n) in a cell nucleus occurring due to failure of segregation of chromatids at the time of cell division. A cell nucleus showing aneuploidy has more or less chromosome number.

Assuming n to be the number of chromosomes in a haploid cell, following are the possible aneuploidic conditions:

Monosomy = 2n – 1
Nullisomy = 2n +2
Trisomy = 2n + 1
Tetrasomy = 2n + 2

Final answer :
a. Aneuploidy