Question

ln the hexaploid wheat , the haploid $(n)$ and basic $(X)$ number of chromosomes are
A. $n = 21$ and $X = 21$
B. $n = 21$ and $X = 14$
C. $n = 21$ and $X = 7$
D. $n = 7$ and $X = 21$

Answer 1

Hint: Wheat is a globally important grain. Wheat belongs to the genus Triticum which is included in family Poaceae (earlier Gramineae). There are three species in the genus Triticum, namely diploid, tetraploid and hexaploid. The number of somatic chromosomes in this species were $14$ , $28$ and $42$, respectively .

Complete answer:
Haploid number: It represents half the number of somatic chromosomes of a particular species and is denoted by n. Since the haploid chromosome number is usually found in gametes, it is also known as gamete number.
 Diploid number: It refers to the somatic chromosome number of a species and is represented by $2n$. Since the diploid chromosome number is found in zygotic or somatic cells, it is also known as the zygotic or somatic number.
 Basic number: The gametic chromosome number of a true diploid species is called the primary number. This is the minimum number of haploid chromosomes in each species, denoted by x. For example, the basic number of wheat is 7, while the haploid numbers are $7$, $14$ and $21$ for diploid, tetraploid and hexaploid species, respectively.

Hence, the correct answer is option (C).

Note: They are the same in true diploid species, but different in polyploid species. Thus, basic numbers can be haploid numbers, but not all haploid numbers can be basic numbers. The number of chromosomes also vary from species to species.
Bread wheat (Triticumaestivum) is primarily a cultivated species belonging to the hexaploid group. Other types of culture are T. monococcum in the diploid group and T. turgidum in the tetraploid group.