Question

Root cells of hexaploid wheat has 42 chromosomes. Which one of the following is the basic chromosome number of wheat?

• A. $42$
• B. $21$
• C. $7$
• D. $14$

Answer 1

Answer: (C)

$7$

• According to the question, the hexaploid wheat species (Triticum aestivum) have 6n = 42. Ploidy level of an organism shows the number of complete basic chromosome set which means that hexaploid species has 6 sets of basic chromosomes. Thus, basic chromosome number for 6n = 42; x = 7. The correct answer is C.
• If the species was monoploid, it would have 6n = 42; x=42; but it is hexaploid which makes option A incorrect.
• Haploid chromosome number is the one present in gametes of that organism; gametes contain half the chromosomes of the somatic cells. Thus, the haploid chromosome number of hexaploid wheat is 21 which option B incorrect.

If the basic chromosome number is x = 7; the diploid species have 2n = 14 but not a hexaploid species; option D is incorrect with respect to a hexaploid species.

Therefore, the correct answer is option C.