Question

In Pisum sativum, there are 14 chromosomes. How many types of normal homologous pairs can be prepared?
A. 14
B. 7
C. ${2^{14}}$
D. ${2^{10}}$

Answer 1

Hint: Pisum sativum, the common pea (also known as the garden or field pea), is an herbaceous annual in the Fabaceae (formerly Leguminosae) family.

Complete Answer:
- Pisum sativum was one of the first plants for which the mitotic karyotype was recognized and the cartogram assembled. These achievements were required owing to the physical mapping of P. sativum, providing data for evolutionary approaches and breeding programs.
- In spite of significant advances, precise morphometric characterization of chromosomes and karyogram assembly of P. sativum have become a topical problem. The present study proposes an unambiguous classification for the chromosomes of P. sativum, based on classical cytogenetic rules and chromosomal DNA amount.
- Cytogenetic procedure yielded mitotic cells showing morphologically preserved and stoichiometrically stained chromosomes. Twelve mitotic cells were selected, and the mean values for total, short- and long-arm lengths and DNA amount were measured for each chromosome.
- Chromosomal DNA amount fully correlated with total chromosome length, whose value proportionally decreases with the amount of DNA. Considering these data, all seven chromosomes could be unambiguously identified, yielding a new cytogenetic classification for P. sativum chromosomes.
- Moreover, the chromosome pairs were ordered according to the classical cytogenetic rule for assembly of karyograms. Since P. sativum is considered a model plant, it was possible to correlate the newly outlined karyotype with other cytogenetic data and linkage groups.
- In Pisum sativum, 2n = 14, therefore 7 number of chromosomes are present.

Therefore, from the above explanation the correct option is (B) 7.

Note: P. sativum is an herbaceous annual, with a climbing hollow stem growing up to 2 - 3m long. Leaves are alternate, pinnately compound, and consist of 2 - 3 pairs of 1.5 - 8cm long large leaf‑like stipules.