Autotetraploid refers to a tetraploid organism with four sets of chromosomes from the same species, denoted as 4x. Nullisomy involves the loss of both chromosomes from a homologous pair, represented by 2n-2. Monosomy means missing one chromosome from a pair, symbolized as 2n-1. Allohexaploid is a hexaploid from three different species, shown as 2x(1) + 2x(2) + 2x(3).
Correct Answer
The correct matching is option (B): (A) – (I), (B) – (III), (C) – (IV), (D) – (II).
Term Explanations
Autotetraploid (4x)
An autotetraploid arises from chromosome doubling in a diploid (2x) species, resulting in four identical chromosome sets. This polyploidy enhances vigor in plants like potatoes.
Nullisomy (2n-2)
Nullisomy occurs when an entire homologous pair is absent due to nondisjunction in meiosis. It severely impacts viability, especially in animals, but some plants tolerate it.
Monosomy (2n-1)
Monosomy results from losing one chromosome of a pair, leaving a single copy. Examples include Turner syndrome (XO) in humans, causing developmental issues.
Allohexaploid (2x(1) + 2x(2) + 2x(3))
Allohexaploids form from hybridizing three distinct diploid species, each contributing a genome. Bread wheat (Triticum aestivum) exemplifies this with A, B, and D genomes.
Options Analysis
| Option | A Match | B Match | C Match | D Match | Correct? |
| (A) | I (4x) | II | III (2n-2) | IV (2n-1) | No |
| (B) | I (4x) | III (2n-2) | IV (2n-1) | II | Yes |
| (C) | I (4x) | II | IV (2n-1) | III (2n-2) | No |
| (D) | III (2n-2) | IV (2n-1) | I (4x) | II | No |
