Question

A plant species A has a diploid chromosome number of 12 Another plant species B has a diploid chromosome number of 16. The allopolyploid developed by hybridization of A and B shall have a diploid chromosome number as:
(a) 14
(b) 28
(c) 40
(d) 56

Answer 1

Hint: Allopolyploids have genomes from two or more species. Several of our crop plants are allopolyploids. Production of allopolyploids has attracted considerable attention; the aim nearly always was the creation of the latest species.

Complete step by step answer:
A polyploid containing genetically different chromosome sets from two or more species is understood as Allopolyploid. Most natural allopolyploids have 2 copies of every genome. This has led to speciation or evolving of the latest species from existing ones. Genome allopolyploidy is the condition where two or more distinct genomes from the same or different individual are brought together through hybridization between two or more species followed by doubling of the resulting hybrid. Thus, offspring arising from A and B were 2nA + 2nB constituted from nA+nB gamete. Then the allopolyploid developed after the hybridization of A and B shall have a diploid chromosome number as 28.
So, the correct answer is, ‘28.’

Additional information:
- Polyploidy is the state during which a normally diploid cell or organism acquires one or more additional sets of chromosomes.
- The polyploid cell or organism consists of three or more times the haploid chromosome number.
- Polyploidy arises because of the results of total nondisjunction of chromosomes during mitosis or meiosis cell division.
- Chromosome doubling of the hybrid produces an allotetraploid which has two copies of every one of the 2 parental genomes which as a result bivalents are formed within the allotetraploid thanks to pairing between homologous chromosomes or autosyndesis or homo- genetic pairing which makes it fertile.

Note:
- The Brassica belongs to the Cruciferae and consists of both diploid and polyploid species.
- Dysploidy could also be defined because the condition where the basic chromosome number differs within a population or species.