Q.14 Of the two diploid species, species I has 36 chromosomes and species II has 28 chromosomes. How
many chromosomes would be found in an allotriploid individual?
(A) 42 or 54 (B)46 or 50 (C) 74 or 86 (D) 84 or 108
Allotriploid Chromosomes in 36 & 28th Diploid Species: 46 or 50
Species I (2n=36) and species II (2n=28) form the basis for calculating allotriploid chromosomes, where the correct count is 46 or 50.
What is an Allotriploid?
An allotriploid arises from hybridization between two diploid species, combining two haploid sets from one parent species and one haploid set from the other. For species I, the haploid number n1 equals 18 chromosomes (36/2). For species II, n2 equals 14 chromosomes (28/2).
This results in two possible configurations: 2n1 + n2 = 36 + 14 = 50 chromosomes, or n1 + 2n2 = 18 + 28 = 46 chromosomes.
Correct Answer Explanation
The correct option is (B) 46 or 50. An allotriploid (3n) inherits three haploid genomes total from distinct species, unlike autotriploids from one species. Sources confirm this pairing yields 46 (one full set from species I, two from II) or 50 (two from I, one from II) chromosomes.
Analysis of All Options
- Option (A) 42 or 54: Incorrect; 42 (21+21) suggests unrelated haploid sums, while 54 exceeds triploid range without matching combinations.
- Option (B) 46 or 50: Correct, as detailed above matching allotriploid formation.
- Option (C) 74 or 86: Incorrect; these approximate doubled triploids (e.g., ~2×36 + 2×14), resembling allotetraploids (4n).
- Option (D) 84 or 108: Incorrect; 84 (2×36 + 12?) and 108 (3×36) indicate hexaploid or unrelated multiples.
Option Comparison Table
| Option | Chromosome Counts | Why Incorrect/Correct |
|---|---|---|
| A | 42 or 54 | Does not match haploid sums (18+14 variants) |
| B | 46 or 50 | Matches 2n1+n2 or n1+2n2 |
| C | 74 or 86 | Suggests 4n allotetraploid levels |
| D | 84 or 108 | Indicates higher polyploidy (6n) |
Key Concepts in Polyploidy
Allopolyploids like allotriploids combine chromosome sets from different species, often via unreduced gametes. Triploidy (3n) typically causes sterility due to uneven meiotic pairing.
